Mike said:
Are DOS programs installed differently than Windows programs,
especially since XP doesn't have DOS?
Yes, but it has nothing to do with XP's not having DOS.
If so, what's the difference?
Installing a Windows program normally involves bunch of things: copying the
executable file(s) and supporting files to a folder on your hard drive,
copying dll files to \windows\system32, creating entries in the registry,
creating shortcuts in various places, etc.
Installing a DOS program normally involves only a single thing: copying
program's files (often just a single executable file) to a folder on your
hard drive
Which one is more likely to screw up your computer - DOS programs or
Windows programs?
Neither. If a program screws up your computer, it's because it was either
poorly-written or written with malicious intent. Either of those can be true
with both DOS or Windows programs.