Looking for some up to date and timely advice and/or instruction:

I have a desktop PC. Running Windows XP Pro with SP3.

The hard drive was set-up with 3 partitions:

C:\ is the primary and is 47.5 GB
D:\ is the 2nd partition and is 90 GB. All my documents and photos go there.
E:\ is the 3rd partition and is 92.5 GB.

Plenty of free space remaining on D and E.

However, the C:\ drive has only 127 MB remaining.

It needs to be defragged (the PC tells me) but the Microsoft defrag program requires 15% free space (7.2 GB) to run.

The PC says to delete some unneeded files and try again.

When I look at the content of the C:\ drive I do not know what files are needed or not needed. I simply do not know where to start deleting.

Suggestions please.