What motherboard do you have? you might have no choice but to use VM's depending on the driver support for Windows XP.
Something else to keep in mind, unless you use 64bit Windows XP your going to be limited to around 3gb of your 24gb of ram when using XP.
Are you not going to spend all day booting between different OS's if not? Your in Windows 8, your first call of the day is about Windows XP, so you boot in to XP, your next call is about Windows 7, so you boot in to that, then next your back to XP... i can see that getting annoying fast if your getting a lot of calls.