Internet Cafe', Public Library and Schools with "locked" PC's are usually accessible...
If you can MODIFY the BIOS to boot from USB, CD or DVD.
Insert your USB Boot image (ISO). How...See my instructables...
The BIOS (Basic Input-Output System) is a small piece of code 'burned' into a EPROM/CMOS (Erasable Programmable Read Only Memory). This is the hard coded instructions to "boot" your PC.
Even "locking" the BIOS is no longer safe as "Flash" programs can 'reprogram' most any BIOS. Shorts or restes can 'fry' and many sites offer replacements/swaps.
Computers all have files. File systems are the way data is encoded on the hard drive. It's not encrypted nor protected except for EFS or secured shadowed and hidden file systems using triple DES and PGP.
Press F2 or F10 as the reboot prompt asks.
Modify as below the "Boot order"
Insert a CD/DVD or USB boot drive and your in!
(see instructables for ISo images or USB thumb drive)