Firstly to download GMATPrep or to fix an appointment, you need to register yourself here
The name with which you are registering cannot be updated once you are through with the registration, so be careful with that.
Use the exact name available in proper ID acceptable by GMAC. For indians, its the passport. Click here to the list of acceptable ID Proofs.
Your names in passport and as given in the GMAT registration when put up in order should both match.
Follow this order to register yourself for GMAT
Given Names : AAA BBB
First Name: AAA
Middle Name: BBB
Last Name: XXX
You can either use middle name or give it as first name as well. The point is if you put up both the names in order it should be like this
Passport Name: AAA BBB XXX
Registration: AAA BBB XXX
The intention of the post is to be cautious while registering. I found the mistake two days before my first GMAT appointment and had it corrected with the help of GMAT Customer Care and luckily avoided the last minute panic. Though I was very tensed whether there would still be any problem at the test center.