My p/c is so slow ,wondering if its because there are 3 people on the p/c?

the 3 people have their own sites

D'you mean there are three user profiles on the machine? Doubt if that's anything to do with it. You could do with a little housekeeping, I suspect. Get rid of programs you don't use, run an anti-virus, run an anti-malware, try something like Advanced WindowsCare (free) to tidy up rubbish, do a defrag. All these will help. You might also wish to go online to www.crucial.com for a free review of your particular RAM setup and recommendations as to how you could add more to speed it up - you don't have to buy from them.

Hope this helps.

Nah probably not. Could be because of how many programs you are using, some virus software may slow down your computer also.

download CleanUp! or CCleaner they can help sometimes
defrag ur computer can speed it up also

It is most likely a matter of a build up of spyware on your system. Ad-aware 2007 will get rid of the spyware and CCleaner will get rid of the clutter and other things that can slow down your computer.

Adaware 2007 = spyware removal (free)
http://www.lavasoftusa.com/

CCleaner = registry and organizer (free)
http://www.CCleaner.com/

It is probably because your harddrive is packed full of all the users documents and files, videos and est.

What i suggest is that you use a Interent Security program (like Norton 360 or McAfee, which i know can do it) to Defragment your harddrive, what this does is it uses all the space in the harddrive and therefore frees some space up that otherwise would be lost.
Also ask all 3 users to delete all there un-needed files, and videos that take up lots of space, so use a memory stick or a DVD disk (which has 4.7GB) to store some of the files.

I would also delete some programs that you possibaly downloaded a long time ago and are unused and taking a lots of space up.

Also it wouldn't hurt to scan for virus and spyware, because that could be a problem, as if one person download it accidently it effects all of the computer.

Because It's not properly installed that's all,just watch the YouTube Video Below and it might be able to help you!!!