You're correct - the file should have been changed while you were working if you weren't actively saving at the time of the crash.
If the file's not too big I could take a look at it - see if we can rescue anything for you.
You could also try deleting your ArtRage.prs file, found in:
Documents and Settings\<your name>\Application Data\Ambient Design\ArtRage 2
And double-check you're opening the painting file with the same version (or later) of ArtRage you used to create it.
But XP shouldn't be hanging either. With a hang, and a file corruption, you could well have a hardware problem - hard disk or maybe motherboard.
AndyRage's mantra for graphics engine code:
"Sure - how hard can it be?"