UHUH?
Isn't that obvious nihil?
how is it obvious, users are still working on pc's ranging from win 2.1 to win XP, Not sure about registry's in pre win 95 machines but it makes a differance, work on an NT vbased machine compared to 9x system big differance.

The first thing to do is check your task maager for any abnormal activity. Ad aware and spy bot will deal with these annoying programs (mostly net downloaded things, gator and the like)

If there is anything useing a great deal of resources check it out, it may not be legit . Several virII can be picked up this way, likewise malware.

If this dosn't turn up anything check your HDD space. Windows Xp likes 15% free to do all those wonderfull things it does. Even with 1Gb of ram my machine likes to have massive amounts of free HDD space. I mean after all it is a MS OS.

Uninstall all those programs you installed but never really got around to useing. May not be making a differance but it is general PC maintenence that helps in a ll area's with your PC use.

As was said earlier clear your IE cache cookies etc... blah blah.

Check your virtual ram settings, they shouldn't have changed but some pople like to screw with things they shouldn't. Set it either to let windows configer or use this simple formulae

minimum virtual ram = 175% of actuall ram
maximum = 200% actual ram

this is a safe bet to help out with certain memory problems all windows OS seem to have on occasion

SCAN DISK DISK DEFRAG, run these regularly. Why don't people do this. It takes a while but it's worth it. It is amazing how much a defrag will help (Especially on FAT 32 HDD partitions)

Listen to your computer, if a bearing has gone in a fan this will affect it's cooling therefore performance. Check it for temps, most mobo's come with software but if not go to your manufacturers website, there will be a software app for this (Unless it's real ancient or real cheap) sorry I don't know f any all round tools for this but they are available.

Driver updates and windows updates, these are important, but probably not your issue.

After doing all these lovely things it's time to edit your startup stuff.

MS Config is a built in utility for windows to get into the registry easy and remove startup programs. For a beginner I would suggest ONLY editing startup stuff. Get rid of non essentials. If ya remove something and your Nortan dosn't apear next restart You probably removed nortan from your startup re-enable it. This is how I run my pc normally I just continuously remove annoying things from the startup and keep my machine clean I forget about the registry unless I havea virus or malware infection thing.

So go forth and be tech. Save yourself some money.