You need some kind of utility to enable the custom Toshiba functions.
Usually in Windows Vista and 7, its the Value Added Package, but for XP you need Common Modules and/or a Wireless Hotkey utility.
XP is being phased out by Microsoft this year, so it may be difficult to find compatible XP drivers for the new Models.
Is there a reason you need XP?
Windows 7 has an "XP Mode" that runs XP inside of Win7 using a virtual machine.
You can use XP Mode to run programs that have problems running in Win7.
http://www.microsoft.com/windows/virtual-pc/download.aspx