Hello.
You should be able to uninstall the LabVIEW run-time engine by going into National Instruments software in the Add/Remove Programs list in Windows.
Note that I don't think you can (or should) remove it if you have the same version LabVIEW installed. If, for example, you have LabVIEW 7.1 installed, along with its runtime engine, it is OK to uninstall the LabVIEW 7.0 runtime engine, but NOT the 7.1 one.