I hear that when you play a Windows disk backwards, you hear Satan.
However, even more scary is that if you play it forward.... it installs Windows.

Seriously though.
Could be a 32 bit vs. 64 bit issue. Which versions do you have?
Also is it a legit version? A buddy of mine had issues with cracked 64 bit Ps and had to 'purchase' the 32 bit version for his 64 bit OS.

With great power comes Awesome irresponsibility.