Ed,
Are you using the same 6501 device on both the XP Home and XP Pro computers? Are you using the same VI on both computers? What LabVIEW and DAQmx versions are you using?
Can you give more details about what you mean when you say it appears to be running slow. The 6501 is software timed so this means that depending on how you have it set up, it will only return data for each time you call the Read VI. If you have 2 seconds of timing in your loop with a DAQmx Read, then it will only read once every 2 seconds. Can you post of screenshot of the code you are running?
You can also try reading the signal using the Test Panels in the Measurement & Automation Explorer. You can access these by right clicking on your device and choosing Test Panels. Are you able to see correct results using this? Can you post a screenshot of the spikes you are seeing?
Regards,
Chris Delvizis
National Instruments