I don't have XP. But I do have a freeware tool that will fix the desktop backgrounds of icons to the transparent alternative. I have it working on a 98SE. It's stupidly easy to use..... and you can then change the text colour to whatever you like.
If nobody else can suss it out for you internally, I'll mail it. Not only is it stupidly easy to use, it's also ridiculously small too.
Do you have Microangelo On Display on the other system? That comes with built in transparency support. Which might be why.