I don't think its the joystick because that works fine on my lapton which is running XP pro. I switched to XP pro on my desktop but the x45 showed the same problems as when the desktop was running vista.
I called seitek support went thought various solutions with one of their guys but he said he need to speak to a collegue and this is what they both came back with:
Hi,
Further to you call regarding your X52 not functioning on your Vista PC I have spoken about the issue with another colleague. He has suggested that bearing in mind the X45 worked on your laptop that the problem lies with your motherboard. This error can sometimes occur with our devices and the most common culprit are nvidia motherboard chipsets. Of course the crucial test for this would be to test the X45 on a Vista PC other than your own, that possesses a different motherboard. However, your case does fit the symptoms of a motherboard issue.
I also found a similar issue on our forum. The solution on there, and the one suggested by my colleague was to purchase a PCI USB for your PC. A PCI USB card has its own chipset and can, therefore, gets around situations like this where the motherboard's USB chipset is having difficulty with certain devices. Installing one and running the X45 from there should get it going again. A PCI USB card usually costs about £8.
If you want to see the forum entry then here is the link;
http://www.saitekforum.com/showthread.php?t=13874