screen freezes when switched on showing only loading logo (blue circle)

am using dell studio xps 16 laptop with windows vista 32 .recently i waas downloading some torrents and had not switched off my laptop for 3 days..when i finally switched it on the desktop shows and then no response.just the loading logo (blue circle)..i can click on only MY COMPUTER logo in my desktop..and can access the drives .but when the left is pressed the lading logo appears again..basically i cant access any shortcuts other than MY COMPUTER.i tried to click on organize drop down menu to c if any hidden files like recycler or something.but then again the screen is stuck with
that blue logo.
i used ccleaner to do the necessary cleaning ( in safe mode of course).used system restore to go back 3 days and still no result..

I suggest a virus scan.

i have done even that using the latest update of avast ..but no use..
when the desktop appears and i click on start it says that this program is not responding and it would if you wait for sometime..when i click on ok the screen freezes and it never responds.i have even done a malware scan using malware bytes but still no result..is there any other way to fix it other than re installing windows?

i have done this
MSCONFIG> choose selective start> load start up items> goto services>hide microsoft services> disable everything else> REBOOT
and it seems to be working
but i still cant figure out how to find the culprit program who is causing this trouble

now that i have done the safe boot my avast and some other functions are disabled in "normal start up" is there any way to bring it back ?

From msconfig, start re-enabling the services one by one until you get the error again.

i have tried that out but it didnt seem to work .so i gave a normal boot ..then the system was back to normal but only problem is that some services like avast dosent function

Try this: http://www.vistax64.com/tutorials/66978-system-files-sfc-command.html

it did not find any violations

I assume you enabled everything in msconfig.exe.

You can try downloading microsoft security essentials and letting it do a scan.

You can also download microsoft fix-it and try the various tests.