I would recommend Quick Unpack - handles UPX, ASPack, PE Diminisher, PECompact, PE-PACK, PackMan, WinUPack and more
Code:
http://programmerstools.org/node/475
a load of other specific unpackers can be found here:
Code:
http://www.absolutelock.de/construction/releases.html
EDIT: FileDETECT detects a linker inside the EXE as
Watcom WLink