A new install of XP leaves it open to Worm and other infections that an antivirus will not stop. (Hint: Blaster and the others.)
One such bug would create some number of 4 gigabyte files.
I'd go bug hunting.
I have successfully installed WinXP Pro (upgrade)on my 2.4 GHz P4 PC. The previous installed OS was Win98 SE, and I deleted "C" partition and formatted new one in NTFS. Once completed, I converted 'D' partition to NTFS by right-clicking>Properties>Format. After completing and checking properties, 67 MB of disk space is shown as used. My hard drive's capacity is 120 GB with 'C' partition = 30 GB and 'D' = 90 GB. Is this normal? This is my first experience with WinXP.