There seems to be a problem with Microsoft’s Windows 7 XP compatibility mode.
Due to the fact that this is build on the virtualisation technology built-in with the processors. It points to the AMD-V or INTEL-VT technology. These hardware virtualisation is not builtin into all pc’s , or is builtin but can’t be enabled cause the option is not available in the PC’s BIOS (which is a nasty thing to forget
So if your pc can’t use or have these technologies you won’t be able to use the XP Compatibility mode. However you could always install VMware Workstation perhaps even player to have your old Windows XP installed as a VM and run you “old” programs on it!