What would the converter cost? I'd get a new drive as they're not really expensive especially the smaller ones like the 250 gig.
I have a 500 gig drive and it's partitioned to 250/250 as the C: and the D: drives. C: is for boot and OS and the D: drive is storage. What happens to the C: drive doesn't affect the D: drive so my data stays intact.
I'm getting another 500 gig drive for my Win 7 64bit OS and I'll partition it the same, 250/250.