Well, as I can somewhat understand your frustration, I also can understand why some things aren't working.
For one thing, when you upgraded from Win 95 to Win 98, it didn't change alot, yes I know that it added a lot of features, but it still had DOS, and it still was a 9x kernel. When you upgraded to XP, a few BIG things changed. For one, you don't have DOS, so, any DOS programs might not work in XP. Two, you don't have the old 9x kernel anymore, you're running on an optimized NT kernel, so that makes some programs that were written only for the 9x kernel simply stop working. Three, (and maybe the biggest change for older programs) you don't use .vxd files anymore(virtual device drivers) so any program that relied on those, will not work in XP. There are some options as far as trying to use the compatabilty modes, but that works mediocre at best.
The best choice would be to either clean install XP, and buy updates/versions for your software. Depending on the software, you might be able to find a freeware replacement, or inexpensive alternative.
Or, you could just revert back to Win 98 if you simply HAVE to have those programs.
Then, later when you get that HDD, just dual-boot between Linux and 98 or XP.
David