HP Pavilion Laptop Freezes Almost Immediately After Startup?

i have a hp pavilion dv3 laptop, 13.3", which runs on windows 7. it has an intel core i5 and 4 gb of ram with 500 gb of memory. it's very new - i only bought it about a month ago, and up until a few hours ago it was running fine. it has been very fast and responsive, and i was careful to not download a load of junk or anything that might slow it down. i used it this morning and it was fine, but since i turned it on this afternoon it has suddenly begun running slowly. when i turn it on i can enter my password and get into my user account, and everything loads fine, but when i try to do anything it will just freeze up and refuse to respond. i can't even right-click and refresh, or click on the taskbar. i just get that little blue spinning circle to infinity.the laptop is running okay in safe mode, which i am in right now. i'm trying to rack my brains to remember what i could have done to mess it up, but nothing comes to mind. last night i downloaded aim, but that didn't seem to have changed anything this morning. when i used the laptop before it started freezing, all i did was watch a few Internet videos and then turn it off again.

when i realised it was freezing, the first thing i did was to turn it off and restart in safe mode. i went to control panel and removed the password to my user account (irrationally, i was getting paranoid about being locked out), which i hope didn't confuse the poor laptop. i then restored it to an earlier date 2 days ago, but it still froze about three minutes after turning it on, and my password was still enabled. after that i went to start > run > msconfig and disabled all the startup items, but the laptop still continued to freeze upon startup. then i unplugged the battery and just ran off the power switch, but it's still freezing! then i started to despair and tried to run a registry cleanup, but i figured it just looked like a scam or a virus so i decided otherwise. i use avast! free antivirus, and i ran a scan, but that didn't find anything.unfortunately, i live in a very hot, dusty country. recently quite a lot of dust was getting into the room where i keep my laptop. i was worried that the laptop might have been getting dust inside it. but i have another older laptop which doesn't seem to be affected at all?i did make backup discs when i first got the laptop, but i only want to use them as a very last resort.