If you want to use Windows 7 Xp mode you need to have PC with Hardware Virtualization support. To know whether your PC support this or not

1. Go to Securable

2. Download the application

3. Run it (No need to install)

It will display the Processor and 3 features of it

1.  Maximum bit length of the processor

2. hardware D.E.P. (Data Execution Pretension)

3. Hardware Virtualization – The one you need to know

Also do you want to know what is Hardware Virtualization ? read a post from  DESKTOP VIRTUALIZATION