When installing an application in the Windows XP VM, make sure to install it for “all users.” Usually the install will place a shortcut under “C:\Documents and Settings\All Users\Start Menu\Programs\.”
Shortcuts added in the Windows XP VM to “C:\Documents and Settings\All Users\Start Menu\Programs\” will usually be seamlessly added to Windows 7 under Start Menu > All Programs > Windows Virtual PC > Windows XP Mode Applications.
You can manually add a shortcut to the Windows XP Mode application by creating a shortcut to the program in the C:\Documents and Settings\All Users\Start Menu\Programs\ directory in your Windows XP Mode installation.
If the target in the Windows XP VM contains parameters, it may not get published to Windows 7 automatically. Try this in the Windows XP VM:
Add the shortcut to the executable, without any parameters, to “C:\Documents and Settings\All Users\Start Menu\Programs\”
Wait for it to be automatically published to “Windows XP Mode Applications”
Modify the target of the shortcut, in the Windows XP VM, to add back the required parameters.