Well you could "downgrade" to XP.
Also, you can try "compatibility mode" for XP SP2. I have never tried this with Flexi. I have no idea if it will help at all.
I disagree with you assesment of Vista, but that is just my opinion. Regardless of Vista being better or worse, the "software trap" is going to get you and you will have to upgrade eventually. It is frustrating sometimes, but it happens with almost all software.
New OS (Vista) means that you may need new versions of software (Using Vista causes you to have to upgrade Flexi)
and
New software means that you may need to upgrade the OS (such as those wanting to use the 64 Bit Photoshop CS4 being forced to upgrade to Vista)
I like to call it the "software trap". We get it from both sides. The only way to stay ahead of the game is to stay current with everything. It is nasty and expensive sometimes, but that works out great for the software companies.
This is one of the reasons that we "interview" all of our customers about their current software situation. We want to warn customers of incompatibilites before they buy their computers. We give them all of the information beforehand and they can make the best decision for their situation. Sometimes they choose the legacy OS (XP) and sometimes they decide to upgrade their software (such as Flexi), but they know what they have to do going in and don't have to worry about losing time/$$$ scrambling after the fact.