Quick help here please?

Can you fill in more than "not all of my space"?

First possibility is that you are caught with the common problem of two definitions of the same word. WD and other drive makers use the word "Gigabyte" to mean 1,000,000,000 bytes. Microsoft Windows uses that word for 1024 x 1024 x 1024 bytes, or 1,073,741,824 bytes. So WD's 640 GB becomes Windows' 596 GB. With a little allowance for file systems and the Windows install, if your C: drive says its Total Space is around 590 GB and the empty space is 550 GB or so, you have lost absolutely nothing!

If your drive says its Total Space is only about 128 GB, you've been caught by an older problem, the lack of 48-bit LBA support. I seriously doubt this is your issue, but just maybe. Normally this only happens with older hard drives systems (and ALL SATA drives do NOT have this hardware issue) or with older OS's, and I surely expect Win 7 RC1 NOT to have a problem here. But if that is your size indication, there are a few obscure ways that could happen.

If your size appears to be something else (likely between these two), then for unknown reasons your drive was Partitioned to that size. This could be changed if necessary. Or, you could leave it alone and just Partition the rest of the space into another separate drive to use.

Let us know the details.