I don't like getting errors in programs / games that have been working only a few hours earlier.
And yes, i know, it's an outdated game, but when i try to start Postal 2 now, i keep getting the darned Protection Error: Error 103

I've had the problem before (couple a years ago) and solved it..just need a reminder of what i did
No idea googling it because i've done that since yesterday and all i find is someone whining on EA for not helping enough..

With Protection Error 103, check your memory. Download and run MemTest.

In addition, after you finish playing a game that is graphic-intensive, restart your PC.

Try it out and post back.