Computer suddenly running slow and freezing frequently..Help!?

Hi,

My computer has been running smoothly for about 4 years now. However suddenly over the last few days, it has started running extremely slow and constantly freezing to the point where the computer is unusable (am using sisters comp to write this).

My norton security is upto date, i regularly defrag etc and look after the computer.

I recently went wireless (security protected). I dont know if this has anything to do with it.

A virus scan revealed a trojan (but was only a low threat) which has been deleted but the computer is still running poorly.

Has anyone got any ideas as to what is causing this? before i reformat the computer?

Any help would be greatly apreciated!!

Thanks

Computer suddenly running slow and freezing frequently..Help!?internet security software

Clean up all junk, remove viruses and check your hardware. This may be a number of things, including your motherboard.

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Computer suddenly running slow and freezing frequently..Help!?moto guzzi

Check out http://www.pcoptimizerprodownload.info

With pc optimizer pro you can safely clean, repair and optimize your computer.

It will help improve your system performance.

Good luck!
Eh, could be any one of a hundred things...