Although this procedure is relatively simple, you perform it at your own risk. You will, at the very least, void your warranty by opening the box, and if you break something then don't blame me.
Secondly, there is high voltage in the TiVo. Make sure it is unplugged before you open it, and DO NOT touch the power supply as the capacitors retain charge even after unplugging.
Thirdly, the TiVo I am using as an example is a Series 3 AU/NZ model. The process for upgrading other Series 2 or 3 models is almost identical, but the layout of the box can vary considerably.
Fourthly, if you have an external TiVo disk expansion unit on your TiVo, this procedure may lose your recordings, though the upgrade should work. The TiVo uses a spanned filesystem and I do not know how this procedure is affected by an external unit. I would suggest you use the TiVo menu options to remove the external unit before performing the upgrade and re-add it after.
There are people in the USA at WeaKnees who will do these tasks for you, at a price, if you do not feel happy doing it yourself (I am not connected to them; however they seem to be the only source of the TiVo parts)
Torx T10 screwdriver - to open the case and remove hard disk
PC with SATA disk interface and two free SATA connectors - to connect the old and new disks
Choosing the disk
A TiVo can support one or two disks, each up to 1TB in size. A normal TiVo will have only one drive internally, plus an external eSATA port for the expansion unit. Therefore, you will likely have a single 160GB or 320GB drive mounted internally, and you can replace this with a 1TB drive which will cost you about US$100. There is no point in using a larger one as the TiVo will not be able to use it (it is a limitation in the disk partition table format used by the TiVo).
The disk you buy needs to be a SATA disk, preferably with some on-board cache, and rated for PVR or NAS. Other SATA disks will work, but will weak out more quickly or be more noisy. NAS-rated disks will be about 5400rpm, not 7200rpm and have some on-board cache.
If you have problems obtaining a disk, WeaKnees can sell you one either blank or pre-loaded with the necessary software to make the changeover very simple.
Choose a method
You have several choices in how you upgrade, depending on how much you want to preserve.
The simplest is to replace with a virgin TiVo disk. In this case, you will need to reconfigure it as if it were newly purchased, as nothing will be set up - back to factory setup. This can be done with a pre-initialised disk from WeaKnees, or by initialising your new disk with a 'fresh install' truncated backup image. The backup image in this case needs to be appropriate for your particular region and model of TiVo; for copyright reasons I cannot post any here so ask me directly or post a request to the Tivo Community website if you want one.
The next is to preserve your current setup and configuration - including season passes, and so on - but lose any current recordings. This is probably the best option if you do not care about your existing recordings, and only needs a single SATA connection on your PC. Ideally, clear all existing recordings on your TiVo before you shut down and open the box.
The final is to preserve all recordings exactly as before. This will take an additional hour and a half to copy the data over and requires two SATA connections on your PC, so that you can do a complete clone of the existing disk partitions.
Step 1: Remove and Backup the Old Disk
Remove the disk
Unplug from the power, then open the case using the Torx screwdriver. The hard disk can be removed by disconnecting the SATA/Power cable, and unscrewing the mounting tray in order to remove the screws underneath. Be very gently with the disk - a hard knock, or static electricity can damage the disk or data permanently.
Back up the data
This is a good idea, even if you are working from a fresh disk.
Shut down your PC, and then connect the Old disk to one of the SATA connectors. Boot up, and run the WinMFS software.
WinMFS should detect the old disk and allow you to select it.
You can now use File/Backup to create a 'truncated backup' (.tbk) file. This is a backup of all the software and configuration, but NOT the recordings. It is worth having for the future in case you ever need to reinitialise a disk when you do not have the old disk on hand. Creating the TBK file is relatively fast, just a few minutes.
Initialise New Disk
If you have opted to NOT preserve your recordings, then you can proceed to initialise your new disk using the TBK method. If you want to preserve recordings, go to the next section, 'Clone Disk'.
Shut down your PC, remove the Old disk, and connect up the New disk. Boot up, and run the WinMFS software.
You should see the New disk in WinMFS as an available blank disk.
You can now use File/Restore to load your TBK image onto the new disk. If you have skipped the 'Back up' stage then you will need a factory-install TBK image to load to the new disk; if not, load the TBK image you created in the previous step.
When the TBK restore finishes, you will be prompted to expand the filesystems to use all the available new space on the disk. Answer Yes to this. If your new disk is >1TB then allow WinMFS to restrict the filesystems to just 1TB else it will not work.
Once this is done, you can shut down your PC and remove the New disk ready to reinstall to the TiVo.
Clone New disk
If you have opted to preserve all recordings, then instead of restoring your previous TBK, you will need ot do a disk clone.
Shut down your PC, and connect up both the Old and New disks. Boot up, and run WinMFS.
You should now be able to see both the Old (TiVo) disk and New (blank) disk.
In WinMFS, run the Clone Disk command to copy from the Old to the New disk. Be very careful to make sure you're copying in the right direction from the correct disk! If you accidentally overwrite your Old disk then don't worry, we took a TBK backup earlier, though you'll still lose all your recordings.
Running a copy of a 320GB disk that is mostly full of recordings will take about 1hr 30min.
Once the clone is finishes, you will be prompted to expand the filesystems to use all the available new space on the disk. Answer Yes to this. If your new disk is >1TB then allow WinMFS to restrict the filesystems to just 1TB else it will not work.
Once this is done, shut down your PC, and remove the TiVo disks.
Place New disk in TiVo
You can now mount the New disk into your TiVo, using the screws you removed earlier. Be careful, and dont forget to connect the SATA/Power connector before you close the box.
Test New Disk
Connect your TiVo to power and television set. The bootup will continue as usual; if it stops before the 'Almost there' page then you likely made a mistake initialising or cloning the disk (did you clone in the wrong direction?). In this case, take the disk out and go back to the Initialise New Disk step to load the TBK, then try again.
When the Tivo is started, it should have all the configuration as before (if you did not use the virgin image) and all your recordings (if you used the Clone method).
If you used the TBK method, but did not delete the recordings before starting, then the recordins will appear in your Now Playing list but they will not work. You must now delete them from the Now Playing as otherwise the TiVo will get confused.
At this point all should be OK! You now probably have three times the storage space in your TiVo, and also a spare drive (the Old drive) that you can keep in case the New drive ever dies and you need it to get your TiVo back to life. You also have the saved TBK backup image for future use.
If your TiVo starts up, but the recordings page says "A hardware problem has been detected which needs your attention", mentioning "Error 51", then you need to perform a complete reset and reconfigure. This is done under the Settings menu using the "Delete Everything" option.
The TiVo license follows the motherboard serial number. It is not stored on the hard disk. The Media Access key is stored on the hard disk, but gets downloaded when the TiVo runs its update.
If you are starting from a virgin install image, the TiVo will need to spend a fair amount of time online downloading software updates and guide data, after you've configured the network and channels.
The TBK image is for a specific model and region of TiVo. In other words, do not use a Series 2 Directivo image on a Series 3 Tivo, nor should you use a US/Canada Series 3 image on an AU/NZ Series 3 Tivo. Picking the wrong on will just break it all. This is why you should always take backups where possible.