restore to factory settings in accordance with your user guide. That's in all likelyhood on your hard drive in the Start menu under All Programs -> Dell. If not, you can go to Dell's web site, put in your service tag, and download it.
When you've gotten your system back like you want it, I urge you to get yourself an external hard drive and a good 3rd party backup program. You can set it up to do everything automagically at the time and frequency of your choice. 1 TB external hard drives are about $70 these days and a really good FREE backup program is the Easeus todo backup free which you can download from
http://www.todo-backup.com/products/home/free-backup-software.htm . That can save you a lot of time and frustration the next time something like this happens. Sooner or later it happens to all computers for one reason or another.
Good luck.
I have a dell inspiron mini and it has windows xp. I get on the internet using a alltel wireless plug in. I recently tried to do some cleaning to make computer faster and have evidently messed up something. Alltel wireless plug in wont work, cant get on internet at all. will not let me do a system restore, cant play games like solitaire because they are gone. i dont know what to do. please help. also called alltel and they thought the wireless plug in was bad, but it is not, because it works on my desktop. thanks for any help.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic