We have NI PCI-4351 working in Windows 98.
We are exploring to move to Windows 7 and CVI.
Has anyone this combination and how did you get on?
Compatibility-wise see here. It says the NI-435x driver is not supported in Win7.
You might have to re-code the app with DAQmx, which is supported.
Probably your Win98 machine is an old one. So, another a major source of problems might be the timings.
Your current application might have been running without problems because it is somehow "tuned" for that computer.
The new faster computer will be doing things much faster and in multiple cores.
You might run into some race conditions due to some thread timing issues.
Hope this helps,