How to change HD drive letters

I have recently had to re-install my OS (Win.XP) as I needed to replace a faulty motherboard. Upon installation I realized that the OS was installed on the wrong HD, but since both are exactly the same model I didn’t realize at the time.

Anyway, whether it truly affects the system or not I would really like to switch the drive with the OS, now labeled “Local Disk(E:)”, with the other drive without the OS which is labeled “Local Disk(C:)”.

Is this possible or will all my programs not work because of the change? (All program files installed in E:Program Files directory)

I’m running Windows XP SP2

Thanks in advance for all those who can give me some advice.

-Nick