If you set a system restore point before the installation that killed the machine you might be able to just back out of the corruption. (Use Start->Program Files->Accessories->System Restore). You may not have an appropriate restore point that works, however.
I got corrupted DVD drivers on my Windows XP system. Dell suggested a "repair install" of Windows XP. You set the boot up drive to the CD using BIOS setup, then boot up the Windows XP installation disk. Skip the step with the "repair console", agree to licensing terms, then it will notice you have an existing operating system and ask if you want to just repair the existing installation. Type "R" to repair. This fixes the operating system, but leaves all applications alone.
Dell recommends serious backing up before you attempt this, however. See http://support.dell.com/us/en/kb/document.asp?DN=FA1056993 for details.
I got most of the problems fixed on my machine by first uninstalling Roxio CD software, uninstalling my scanner software, and uninstalling my printer software. Also cleaned out all files and directories and registry entries associated with these packages. Then did a Repair install of Windows XP, then carefully re-installed the latest versions of all my peripheral drivers (I also set a lot of system restore points at each stage so I could back out of installations as necessary). It took about half a day to finally fix the problems, and some minor issues remain, but the system is mostly working again!
