Okay, the language you're using is LabVIEW. You didn't say that in the original post.
Hyperterminal is a terminal emulation program that comes with every version of windows. You can get to it from Start>Programs>Accessories>Communications. But, since you've managed to get communications to work in MAX (Measurement & Automation Explorer and what I'm assuming you mean by NI Instrumentation program), you don't need to try Hyperterminal.
There's a big difference between GPIB and serial. GPIB has standards for electrical, physical, and communication. The communication stardard defines the handshaking and interface management. One management line is EOI. This is asserted at the end of a message. Serial has no standards beyond the electrical and physical. Most serial instruments require some sort of termination character at the end of each command. This is often a carriage return or a line feed. The instrument manual should tell you what it is. In the example that worked, did you see a \n or \r anywhere? A \n is a line feed and a \r is a carriage return. If one of those is the correct termination character, you need to add it to the end of the command. One way to do that is to right click on the string control/constant you're using for the write and select '\' Code Display. You can then type either \r or \n at the end of the command. You can also use the concantanate to String function and use the constants on the String palette. You can also use a VISA property node to automatically append a termination character to each VISA Write but I think the first step you should take is one of the first two options I mentioned and actually get some data.
The problem you're having is common. If you had searched the forum, you would see hundreds of posts on the subject. You might want to take the time to do a search as a lot also have some example code.
