While on one of our client sites on Monday we had found that while doing a test to determine available ethanol in a sample of mash the client's HPLC system recognized the sample but choose the wrong sample method and thus returned the wrong values. The client is using a HPLC 1100 to perform the tests and loads up 6 samples to be tested. The incorrect analysis selection does not happen all the time but is happening. The software has two methods saved but the client rarely ever uses the extra method. Is there possibly a patch required in the software which could explain why the system has one method selected but uses the other? I do not know the patch level which the client has employed on in their software. I do however know the sampling computer is not backed up, and the operating system is not current.