If you get Windows 7 Pro or Ultimate, you will get a free XP licence to run as a 'Virtual Machine' - you need to install it manually though after downloading from Microsoft:

http://www.microsoft.com/windows/virtual-pc/

It features full integration with Windows 7, e.g. a Windows 7 start menu shortcut can be used to start an XP program running under the Windows 7 desktop. You can also access it directly (like accessing a remote desktop across a network, but without the lag). It does take a little effort to set up, but it then gives you the best of both worlds. XP will run slightly slower than if you installed it directly due to the virtuialisation, but the difference is negligable and should be offset by your new hardware anyway.

You can also convert your current XP laptop's hard disk into a Virtual Hard Disk (.vhd) to use as a virtual machine, so you will be able to access your 'old' laptop from within your new one (note this will require re-activating XP on the new hardware, so you can't keep using your old laptop if you do this). This is more complicated (e.g. you have to manually install the integration features), but is still not too difficult. The following site gives instuctions:

http://www.techrepublic.com/blog/wi...ows-7-virtual-machine-with-disk2vhd/3091

I've done both processes many times (and with many operating systems apart from XP), so if you need help, you can PM me for tips.

HOWEVER: I have never needed to use the XP virtual machine for compatability - Windows 7 already has an excellent compatability mode for XP built in (unlike Vista). I had one flight simulator called "Wings Over Israel" that stated it could ONLY be run on XP, but it actually worked fine under Windows 7 using compatability mode. So my recommendation would be to get Pro/Ultimate just in case, but don't worry about using virtual machines unless you actually have issues with the default compatability mode.

Hope this helps!