Windows 7 - 750GB drive shows as only 365GB drive - where's the rest of it?

I bought a hard drive enclosure so I could use an old (year old) 750GB drive as a place to store backups - the USB drive I've been using will only hold one system image at a time, and if I end up having to reinstall Windows using it I invariably lose some files.

I used a 3rd party disk utility program to wipe the drive- but it only shows about one half of what the drive is labeled as.
I went into diskpart and listed the volumes and it says the same! Now where could this other 300 odd Gigabytes have gone?

Post a screen shot of Disk Management.

Do you mean start>administrative tools>computer management?

Yep; and then poke "Disk Management" on the left side of that window.

yeah.... in that left pane -> Disk Management

Duh, no coffee yet - here it is:

For some reason, I can't post an image from the screen shot - I've done it and it's now an image in paint, but even copy then cntrl v OR simply right click paste will not copy it over .. what am I doing wrong??

I was just looking at disk management, and it shows unallocated space as 349.87 and the 2nd as 348.77 primary, healthy NTFS partiton.

Can I simply delete the 348.77 volume, then reformat the disk?

You need to add that unallocated space to a partition.

But don't do anything until you post a pic of Disk Management. The tool you need can't be determined until we see the pic.

To post a pic, use "go advanced", then "manage attachments", then browse to your saved picture and choose "upload".