Sorry for not getting back to you, i had a lot of irons in the fire. And no need to apologize, as we all began as newbies and i have much to learn as well.
The questions were, Open Windows Explorer (hold down the Windows key and tap the E key and let both go) and see how many drives/partitions are shown there. What size are they? (go to View up top and click on Details). Then and navigate in the C drive and right click on the WinNT folder and select properties...this will report what size it is.
As for your last question, (i assume that you are indeed speaking about your XP backup and not the System Restore files), it does sound this that is the answer to your space problem, and you can delete the backup, but it may be that you have only one backup, that being your entire C drive. In any case, i would recommend you save at least your personal files somewhere first. You can then go to Start> Programs>Accessories>System Tool and launch Backup (or, hold Windows key and tap R key, type ntbackup.exe and hit enter). Then choose Advance Mode and hit the Restore and Manage tab up the top, right click on the backup and choose Delete catalog. Then check your space again in Explorer (press the F5 key to refresh the window).
You can also delete all the System Restore points except the last one by right clicking on your C drive, then hit Properties and then Disk cleanup and then the More Options tab up the top. System Restore is down the bottom.
I would recommend that you buy an external hard drive if you can, or an external enclosure to put a spare drive in, and that way you can just plug it in the USB and backup files to there.