Morgan, do you happen to have a disk imaging program in your arsenal ? ?
Reason i ask is the safest way to do this and the least messy would be to make an image of the 127G partition check the archive and burn it to DVD.
Then wipe the 300G and use the HDD manuf. utilities that shipped with the drive to allocate the total space and set it as active.
Then run your image program to restore your original contents to the full HDD.
There are programs that can do this and say they do it well such as partition magic etc. but in my experience i don't trust the results...learned the hard way.
The other option would be to let XP allocate the free space and create another partition which you could now use for storage.
Keep in mind it might not become the D: drive as physical drives take priority over partitions.
So C: would be your existing bootable drive that contains XP
D: would be the WD80 G
And E: would be the 151G remaining on the 300.
Hope this helps.