Clean up your C: and just make that one a "SOFTWARE" location.
Change the TEMP to D:\TEMP.
Never ever save anything extra in C:\
Basically use C:\ as the OS, D:\ for data.
For winxp, 10G is enough, cleanup all the unnecessary programs,
and files and move them to D:\.
Invest on an external backup drive like 400G for 1000 HKD or so...
just use the system itself as a workstation.
The bigger the OS C:\ , the bigger mess it is. Keep the OS intact
and Program Files\ applications all in shape.
Maintenance is an art and we need to learn how to do it right.