Freezing computer

Hi
I have been sent over here from the Software forum.
I have an Acer Aspire desktop running Vista Home Premium. It is about 18 months old.
yesterday I downloaded Bullzip PDF printer from Download.com and shortly afterwards the PC started freezing. I have uninstalled Bullzip and done 3 system restores to earlier dates. I have tried runnning antivirus scans and spyware scans but it never gets to the end of any of them before freezing. I have tried disconnecting most of the peripherals and have tried starting it in Safe Mode but nothing seems to help
It also sometimes freezes during the early stages of booting up. When it freezes the image left on the screen is often a bit blurred.
I have spent the past 6 hours trying to work my way through the the instructions on the Malware Removal Forum, but I am getting nowhere fast as the computer doesn´t last for more than a couple of minutes before freezing again. I have downloaded the tools suggested onto a separate computer and am trying to install and run them 1 by 1. The Superantispyware never gets more than a few seconds in and the malwarebytes appears to have done a quick scan but could not do an update before running. I cannot get any further tring to install combofix as it does not last long enough.
Is there any hope, or am I looking at a complete re-install?

Thanks

 

Hi Kestrel13!
Thanks for the reply. I didn´t get that far in the list, but I have been trying to install it this morning however it keeps on freezing.
I am beginning to think that it is a harware problem because:

1. It sometimes freezes within seconds of turning on, before Windows has started during the BIOS checks.
2. If it has been left for a while like overnight, it will run for several minutes before the problem starts.

What do you think?

Martin