I was using a disk space explorer and found that Adobe Acrobat was hogging up a whopping 1.22gb on just the frickken installation to auto-repair itself "in case something broke".
The files were located at "C:\Program Files\Adobe\Acrobat 9.0\Setup Files\{AC76BA86-1033-F400-7760-000000000004}", but it may be differ if you changed the installation path.
Sorry, but I cant be stuffed repartitioning my C: just because I'm running low. Wasteful applications like this have got to fuck off.
Give Adobe a swift kick to the nads to remind them how much they suck.
If you're paranoid about deleting it straight off, just move it off onto another drive "in case something breaks" and auto-repair fails.
The main file using up all that space is "Data1.cab". Acrobat seems to be working fine without it, and my computer can now enjoy a bit more breathing room.
There are more uncommon space saving tips here.