Ahh my specialist subject

First things first, just use this little application that will do it all for you http://www.filehippo.com/download_ccleaner/
Top right hand side in blue text click on "download lastest version". Basically this will delete all the crap that every pc gets on it and it will take a matter of seconds or maybe minutes in your case as i do use this once every 2-3 weeks, first time i used ccleaner it got me back 1 gig of hard drive space( thats an awful lot if you dont know) every pc should have this installed i reckon Still use this even if you used what the other guy suggested.
Click on "run cleaner" that will start it scanning and deleting, then after its done it will list everything its deleted and tell you how much free space it gave you, then after that click on "issues" on the left then click on "scan for issues" this will scan your registry for any crap or obsolete files.

Ok thats that done, just note after using this, since it will delete cookies and stuff it will mean all your forums you visit(or anything you type a username password for) will be cleared so you'll need to re enter them on every site and then click on "log me in automatically" agian and it will then start remembering you agian.

You shouldnt have any problems doing any of the above so ill go onto the next thing, click on start bar, select "run" when the box pops up type in "msconfig" without the quotes, then you will get another box come up, click on the "startup" tab at the top and tell me how many boxs there are with green ticks in them? infact even better could you post a screenshot of this box? hit print screen key on your keyboard, open up windows paint, click EDIT then paste, save the pic and post on here and ill tell you what to do from there

Basically its a list of all the things that load up when you turn your pc on, it maybe that you have loads on there, this will effect it if you have a silly amount