Well, I did an upgrade from 98 to XP and it was a bit of trouble, but it was manageable.
First off, do the Upgrade Wizard thingy, (forgot the name) it will look for software and hardware that is not compatible.
For sure, uninstall Antivirus, Utilites like Norton, Partition or Image software, and any others that have WIN9X versions and NT\XP versions.
Get the drivers for your hardware
BEFORE you upgrade. Because if you can't get on the internet how can you get the new drivers, and if you don't have the new drivers how can you get on the internet? Catch-22 big time.
Do a Ghost or Image of your drive before you start so that if it fails miserably you can go back to what you had.
I'm sure I am missing something, but you get the idea. Get prepared before starting, and it can be a not so terrible experience.
On the other hand how long will it take to reinstall all the software you have accumulated over the years? Days, for sure. It would for me, anyways. And don't forget that if you do a "fresh" install that usually means formatting your hard drive. What about all your documents and passwords and favorites and email\isp configuration, and saved email, and Tax and financial data, and pictures and mp3's.... you get what I mean. A lot of work, and you always forget something.
XP took my Cable connection info, Outlook and other office data, Quicken and other data and moved it so that everything worked just fine. Besides a few programs that I had to reinstall every thing worked fine. Yes, I know there are probably a lot of old remnants still in my Windows directory, but if XP is not using them, who cares? I got the space, let them be.
One last caveat: do not convert your hard drive to NTFS right away, let it be for a month or so. That way you can still boot to a floppy and get to your data in a pinch. Hang on that good old DOS boot disk!!
Sorry for the ramblin on
Jon
There is much pleasure to be gained from useless knowledge. (Bertrand Russell)