Hi, Fred.
Are these separate physical disks? If they are two partitions on a single
HD, read on.
You may be thinking of DiskPart.exe and its /extend parameter. That command
is little known, even among veteran Windows users. That's probably because
there are so many limitations on its use that most prospective users soon
find that it won't work in their situation. Search for "extend" in the Help
and Support file; be sure to follow all the Related Topics links because
there are many conditions and "gotchas" that don't appear on the first Help
page you see! And the syntax of the command is NOT always what we expect.
For instance, it won't work on the System Partition - and that's what YOU
need. :>( However, if you have another computer or a friend who will let
you use his, then you can take your HD out of your computer and temporarily
add it as a secondary drive in the other computer. In that other computer,
your System Partition will be "just another volume" to that copy of WinXP.
The "drive" letters will not be C: and D: in that situation, so be sure you
have the right volumes targeted! Boot into WinXP on that second computer,
open a "DOS" window and run DiskPart.exe there after deleting what's now D:.
Use Diskpart /extend to extend your C: to use all the newly-unallocated
space on that physical drive. Then move the HD back to your computer.
Like any powerful command, DiskPart can do a lot of good - or a lot of harm
if it is used incorrectly, so be careful!
RC