Low V. Memory, paging file problem, trojans, HjackThis! Log... HELP!

OK... my pc (specs are below) seems to be sick. And I can't fix it. I've tried Trend Micro's Housecall, Spybot SD, Ad-aware with the VX2 plug-in, CWShredder, CCleaner, I run Sygate firewall... and a few diag. programs. But I still have the same problems.

-when pc loads, it is SLOW... takes many minutes to load and be able to get online
-I get a message saying my paging file is too small or there isn't one. Tried to fix it, no dice. Tried booting in safe mode to do it, wouldn't load past settings (unless it's supposed to take more than like 10 minutes to load)
-space onmy hard drive just seems to be disappearing!! Twice when I booted up, I seemed to have lost 250 MB to nothing! And now, loading up today, it seems to be about a GIG... just gone! And it seems to be growing as I type... nearly 100 MB!!


I don't know what else to do... please help...
Here's my HijackThis! Log:

[log file removed]

 

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