computer freezes when trying to install anything and opening folders

[adz63]

i turned my com on the other day and  now when trying to install anything from comodo firewall to well just everything i have downloaded it freezes my whole pc . i have tried downloading hijackthis to get an analyisist to post here for someone to look at but that too freezes my com and the only way to do anything is hold the power button to turn off and restart . even clicking start and trying to open folders such as documents downloads etc freeze my pc too ... does any one have a solution to this . i have tried system restore to when it worked ok but still the same issue . i use ccleaner once everynow and again and have restored that back to a date when i know everything was working .

vista home premium sp2
acer aspire m1610
intel dual cpu [email protected]
32 bit
2gb RAM

my com did not come with a disk so i cant do a repair install , i have a recovery disk tho but really am trying not to do a clean install as im on a limited data plan and downloading everything including all the sp1-sp2 updates will take up lots of my data

[Allan]

On another site you said this happened after you went to a specific web page and Avast warned you. Please post ALL relevant information here so we don't waste our time trying to guess. Thank you.

[pcrehab]

I just reformated HD and installed windows 7 pro sp1 32bit. Installed updates and now every time i try to install any 3rd party software the system locks up with a black screen. ctl+alt+del does nothing. hard stop with power button and reboot will allow 1 application install and then it goes to **** again. i'm mystified.....

Computer is HP core 2 quad w/2.4ghz cpu and 3gb ram.

I've read on other forums of a possible link to a MS update that "might" be at the route of this but people are not reporting system fail in the exact same manner.