I assume the question is about XP Mode.
XP Mode is not a perfect solution. Because it is a guest OS, there are latency issues with the host OS. With that said, are you certain you need XP compatibility in Windows 7? You could first try running the app with XP compatibility, without using XP Mode.
Most programs (even pre-XP) will run on Windows 7 without the need for compatibility settings, much less the need for XP Mode. XP Mode was designed for legacy 16-bit applications that no longer run on 64-bit operating systems. If you have a 32-bit application that needs compatibility, XP Mode is more than likely not the solution you are hoping for.