Dell laptop Vostro 1520 restore to factory settings problem - please help

Just got my new Vostro 1520 out of the box worked fine and installed the Blackberry OS. The installation of the Blackberry OS seems to have caused major problems with Windows 7. Decided to reinstall back to factory setting. I put in the WIndows 7 re-installation CD and by mistake reinstalled it not to the primary partition C but to some small partition E. Figured out that I made the mistake tried to reinstall WIndows 7 to the primary partition C however the computer does not let me and I keep getting the message not enough space on main partition which is false as I have well over 400 GB of space on it. Not sure what to do? How can I get the computer back to factory settings just like I just got it out of the box again (which was only a few hours ago)? The dell recovery software does not seem to work when I try to use it the computer freezes? Any advise? Please please help....