So i picked up this power supply and found that it did not fit my stupid dell box so i ended up doing the following.
The problem was i got one with 2 connectors not one. but even then it would not of fitted.
Step 1: Size Up Pace for Power Supply.
So just hold it up to space where to put it and see what needs to be cut out.
Step 2: So Cut Out This Section and Away We Go
Cut cut cut...
Step 3: And More Cutting...
and keep on measuring up and cutting and finally we get a hole that is as follows.
and as a suggestion from TheScientist and a very good suggestion should take a file to edges so do not get cut.