A different approach is to try creating a platform (or partition) that employes a different foundation state then rebuilding as 'lean' a system as possible specifically around the audio hardware you want to use. With availability of linux doing this with Linux can be a less $ expensive approach then building a new hardware system from scratch. Particularly when current vid cards are not, as a rule, designed to play nice with dedicated Audio production cards. Nor is this a situation in either Windows or Mac environment that is likely to improve in the near (or even distant) future.
Didn't lead with 'linux' at time of original post because it is not a panacea but it does not appear that OP is making much headway even in diagnosis . . . So? getting rid of windows clutter can help with at least diagnosis
install a sperate partition of linux.... interesting idea...
My suggestion would be to look on ebay for a similar generation Echo Audio card to see if that works. I've just sold 2 working and one faulty Darlas plus a Darla 24 and they went for very low prices.
I think the advice to build a dedicated machine is correct especially if you move to any more modern OS. Keeping in control is all important.
I'm fresh from giving up again on trying to install Fedora 14 dual-boot. After about 4 full-blown attempts, I made a stupid mistake and had to reload from an imige I had made. Having said that, I'm finding Ubuntu on a usb stick is absolutely marvellous as a data recovery and occasional diagnostic tool when things go wrong.
OS on a stick is wild.