6 years in computerdom, is similar to a look at another era.
You may be waiting for the indexation service to do it's job. You may be waiting while reading/writing heavily fragmented files or pagefile.sys. You may be waiting while navigating overcrowded folders.
First thing to do is do some serious cleanup.
Uninstall any programm and applications that you no longer use, and may have forgotten about.
Get and install CCleaner. Have it scan your drive(s) and remove all obsolete files, like accumulated *.tmp files and Windows updates uninstallers.
It works beter and is more thourough than Windows integrated cleanup utility.
Check your restore points, and only keep 1 or 2 of them. normaly, you don't need more than that.
Those 3 steps may free up a few gigs. In turs, the recovered disk space may accelerate your system.
Defragment your drive. I recommend Defraggler for a free solution. You may be interested in Diskeeper if you are ready to pay for a top knotch, set it and forget, server class, smart defragmenter. Defragmenting can take a realy long time, especialy if it was not done regularly.
Both are insanely beter that Windows' bundled speed disk.
Turn off the indexation service.
It takes time, lots of it as well as additional disk space to store the indexes, and if you don't constantly search for missplaced files, you don't benefit enough. (I perform searches like less than once a month)
If you have more than one hard drives, place your page file across the non-OS drive(s) and remove it from the drive hosting Windows. Make it fixed size totaling 4 Gb (installed RAM + page file). (I assume that you have the 32 bits version. reasonable assumption for a 6 years old computer) You'll gain in performance.
Check your drivers. The latest ones MAY NOT be the ones you realy need. In some cases, if you have older video card, like an AGP one, a driver 2 or 3 years old MAY be beter suited. It may be worth it to reinstall the drivers, even if the same version as currently installed.
Check the running services. Several are not realy needed and can safely be disabled.
It frees up resources, both in RAM use and CPU load.
Get a good antivirus like AGV or Avast and scan your computer.
Get a good anti-crapware like Spybot Search & destroy and do a full scan.
This will make sure that you don't have any malware/spyware lying around.
I don't recomend that you try a complete reinstall. It's a last ditch thing to try ONLY after you tryed everything else without success.
Electro, December 2011