After I install IA OPC server 5.1 on Windows XP, when I try "ipconfig" from the command prompt I get an error message saying that is not a valid command. Uninstalling does not help - I have to reinstall the OS before ipconfig will work again. Someone else installed this seat of IA OPC on this PC before and it worked for months (although the PC crashed for other reasons and had to be rebuilt, thus I am reinstalling IA OPC). Any ideas how to fix this?