My megabytes are leaking!

WIN98SE
Comcast cable

Norton AV, AVG, WinPatrol
Windows Update
BitDefender,TrendMicro, Windowsecurity, RAV, SwatIt, Avert Stinger, AdAwareSE, SpyBot SD, SpywareBlaster, CWShredder, Ccleaner
All of the above previously installed and used regularly.

Normally I maintain about 1.5 GB free disk space.
On 13 FEB I had 1.37 GB free space, 15 FEB 996MB, 16 FEB 963, 17 FEB 8:15 905, 17 FEB 8:25 892, 17 FEB p.m. 787, 18 FEB 665, 19 FEB 619, Now 534.

I ran "Files Created" and "Files Modified" checks starting 12 FEB and found nothing unusual. I have the "Show hidden files" box checked.
Nothing strange on the StartUp list, or running in "Ctrl-Alt-Del" box.
DiskAnalyzer showed nothing new that I could determine.

Any ideas on where to look for my "leak"?

 

NM...