Version 7 is fairly old now, and I should think Corel will have stopped supporting it. There's no mention of Quattro Pro 7 at all on their site. It's really tough, especially if it ran fine on Windows 2000 (on which XP is mostly based).
Try running the Compatibility wizard again and try Windows 95 (or other versions of Windows).
If it still doesn't work, try uninstalling it, restart, set up a restore point, then copy the instalation files to the hard disk, and run the compatiblity wizard on the setup file (it may be setup.exe or install.exe or whatever). Use the wizard to install the program under a previous windows version and try running it under that previous version in compatibility mode.
If all else fails, and you want to stick to Quattro, there's a Wordperfect Family Pack 5 (compatible with XP) which contains Wordperfect and Quattro 11, which is much cheaper than the Wordperfect Office Suite. Unfortunately Corel has gone the way of Microsoft in selling their applications in suites and forcing you to pay for programs you don't need.