Sampson,
Thanx for the reply.
I'm not getting a full disk error. I'm getting a file write error. The message also mentions that there may be a disk or a file system error. According to Jerry Honeycutt's book, Microsoft Windows XP Registry Guide, you can export and import Hives as Registry Hive Files. As a matter of fact, he states that backing up Hives is better than using Reg files.
Let me also state that I'm am able to export the remaining three hives, HKCC,HKCU,and HKCR, with no problem.