Random 'pc freeze' after using Combofix

Hello,

I have a pc at home that contain thousands of malwares, and i managed to remove them, thanks to some guidance from this site. (The previous problem was, i cant open/install antivirus programs).

After removing most (if not all) of the spywares, a new problem arose right after i ran a program called Combofix. The guy prepared some script in notepad and ask me to drag that .txt file into the combofix icon. Things run like no problem but at certain point, my pc freeze and need to be restarted.

After restarting the pc, this new problem emerged. U know some old pc had this 'dooo' sound coming out after pressing restart button. As i was using the pc normally (there is no slowing down or antivirus prob whatsoever), at certain point the 'dooo' sound came out and pc froze. As i restarted the pc more and more, the duration of how long can the pc hold on before the next 'dooo and freeze', decreased.

So the best time to use the pc (and carry out all fixing) is the next morning, when i can expect longest duration for the pc to hold on before 'dooo and freeze' (usually about 30 min at most). It started to emerge ever since i did the 'dragging .txt script into Combofix icon' on that day, which failed to finish and also causing the very first 'doo and freeze on this pc.

These are the specs:
-Custom Desktop
-Windows XP Professional Service Pack 2
-Intel(R) Pentium(R) 4 CPU 2.40GHz
-BIOS Award Software International, Inc. P4M266A-8235
-18.7GB QUANTUM FIREBALLlct20 20 Hard Drive
-RAM 512 MB DDR (PC3200) Kingston
-Display Adapter S3 Graphics ProSavageDDR 32 MB
-Sound Adapter VIA AC'97 Enhanced Audio Controller (WDM)
-Network Adapter VIA Rhine II Fast Ethernet Adapter (wired)

I hope this problem doesnt sound too complicated for u. Pls help.