It can be a variety of things... 1st IF you can even run your computer long enough, run spyware checks, virus checks, etc etc. Clean out anything you don't need. If it still doesn't work or if you can't get it to start up, put in the backup disc that should come with the computer. This will erase EVERYTHING in your hard drive and make it new again like when you first got the computer. Hopefully you can transfer the things you want to keep onto a flash drive or another hard drive. If the disc doesn't even run or it doesn't work than it can mean that your hard drive is crapping out. You need to replace your hard drive. Since this is a laptop, it's harder to take apart and change things. You can go to the Geek Squad at Best Buy to let them do it but it'll cost you more $$. If you do it yourself, the new hard drive should come with instructions on how to transfer your OS or old files over [I think]. Or go ask the Geek Squad on how to go about doing it. ALSO, note that since it's a laptop... lots of dust can get into it and cause it to be slow... I suggest you take it apart and use 1 of those air dusters to clean out all the dust and crap in your computer and see if it works any better. If not then proceed to changing your hard drive. Although I'm not 100% sure if it's your hard drive... you should go to the Geek Squad to ask for other options or opinions on what it could be.