Problems using bootcamp?

Okay guys, I'm a noob, and I'm stuck. Help please?

A couple of months ago, I used bootcamp to partition my hard-drive so I could use windows as well, mostly for gaming.

Long story short, my copy of vista turned out to be... crap and I was forced to restore the hard-drive to what it was initially. I really want to re-partition and install win7, but now, when I try to partition the drive, I get this message:

"Back up the disk and use Disk Utility to format it as a single Mac OS Extended (Journaled) volume. Restore your information to the disk and try using Boot Camp Assistant again."

WHAT DO?!

EDIT: for more info, if needed.

Original vista stopped working because it was a trial disk. The trial ran out, and I lost the disk.

Thanks.

In what state is the hard disk now? Is it one big partition are still two partitions?
If its still in two partitions, then you do not need to re-partition it or use the Bootcamp Assistant, just boot off the Windows 7 DVD and erase the existing NTFS partition and install Windows on the blank partition.

The HD is currently in one part, at least as far as I know. See, I ran bootcamp and restored the drive to one part in order to get rid of Vista (possibly an idiotic move, lol) and it seemed to work.

Mainly, I'm not sure what it meant by backing up the disk.