It's actually possible to do exactly what he said, though it's risky. So if you try this, make a backup of all important files.

If you don't mind downloading stuff illegally, get PartitionMagic 8 from PowerQuest and install it. If you do, download the a linux liveCD which comes with gparted preinstalled (I think ubuntu's liveCD does).
If you use the linux liveCD, you'll need to boot from it before you bring up gparted. gparted needs to be run as super user.

From whichever program you're using, select the old windows partition and mark it for deletion, then select the new windows partition and mark it to be extended so it fills the whole drive. Then apply the changes.

Don't know how you change the system drive letter, but this guide looks promising. Or you can google for another guide.