You should post your code. Generally, you can get away with really big and fast periodic data transfers in LabVIEW if you draw it the correct way. Additionally, these tend to be situations where you need a lot of RAM in your computer, so if you have 256MB and are running W2000, it's not going to cut the mustard. To get anywhere with this type of question you need to post OS, RAM, LV version and the code, if possible.