on the laptop would lead you right to support issues for that laptop.

It would have got you to various options for restoring the computer to factory condition. Since You already tried an upgrade I'll just link you to the page for making use of the Restore partition and the F8 key to get there:

http://support.dell.com/support/topics/global.aspx/support/dsn/en/document?docid=336966

Since backing up data files isn't an issue as they have already been overwritten you need to scroll down the page and start with Step 2.

DO NOT skip steps within the instructions.