Hate to say "ditto", but I've been running Win7 64bit for a long time without issues. And since Win7 64bit has gotten so much market penetration, so have a lot of other people.
As Pike said, check out your installation by starting with a freshly downloaded, naked xmplay.exe (no add-ons, no plug-in, no configurations, nothing). Then gradually add those things in and see where it "breaks". I'm confident that's where you'll find the issue.