asus N71JQ-X1 degrading performance

hello all,

i have an asus N71JQ-X1 laptop for almost 3 years now. never had any problems, but recently the performance has worsened drastically. i used to be able to game in 3 windows without any problems, but now even 1 window gets extremely laggy after awhile. i cant even play quite old games without video lag.
i havent reinstalled OS, but i defrag and clean the filesystem regularly.
i disassembled it once about a year ago to clean out dust and dirt build-up. i did that because the fan was too loud often, although i didnt have any performance problems back then.

if i check task manager when it lags, sometimes programs which shouldnt use too much resources actually use a lot, like 1 tab in firefox with plugin-container using 10-20% or even more of CPU. i cant watch high bitrate videos anymore either.

at first i suspected that the hard drive is failing, but i ran hard disk benchmark utilities, and they gave me numbers comparable to numbers on the internet for a new disk. even with a game on and having big lag, hard disk benchmark numbers were good.

any suggestions what to do? how to figure what causes it?
thanks.

 

Check the hard drive for errors as well, to rule out any bad sectors. Sometimes a good ol' fresh install is just what a system needs when it seems to be on it's last leg.

Hopefully it's not related to a virus.