Error when playing Half Life 2 on XP

[Minime88]

The Instruction at "0x241f8977" referenced memory at "0x01cdf5c0". This memory could not be "read".

Click OK to terminate this program.

Ok, when playing the newly released Half Life 2 and Counter Strike Source on XP, it crashes and it comes up with this error message. What causes this error and how do I fix it? :dead:

Thanks!