Games Won't Launch/Load - WTH?

[croSSeduP]

On one of my computers for some reason it comes up with error messages or other failures when trying to launch certain games. My daughter plays Wizard 101. It worked just fine, then all of a sudden it comes up with "error 126" from the Wizard 101 website. Tried their solutions, no help. The weird thing is it was working fine, then just stopped. Now I tried to download Mass Effect 1. It also crashes when I try to launch it. The most recent is tried to download Starcraft 2. Again, it won't even install. It is a Windows XP machine, 32 bit, GTS450 GPU, Phenom 8750 triple core processor. Any help?

 

[MindoverMaster]

I think that is your downfall, XP. For later games, as SC2. I don't think that even comes close to SC2 recommended settings.

As to your old games, not sure.