GMAT Prep & Power Prep Official Free GMAT Tests

I had the same problem on a Windows 7 64bit machine.
I also had installed Nitro PDF Professional.

Steps to make it work:
1. Uninstall Nitro PDF Professional
2. Make sure that the Nalpeiron Licensing Service is gone (Right click on "Computer"->Manage->Services and Application->Services and see if you find it in that list.)
3. If it is not gone, you have to remove it using the command prompt entering the following command:
"sc delete nlsX86cc"
That will delete the service and consequently allow GMATPrep to install successfully.

Hope this helps,
Kevin

GMAT Prep Test is one of the most essential tools in GMAT test prep. GMAT Prep is the Official GMAT Diagnostic Test with Real GMAT Questions.

!	Downloads Section GMATPrep v2 2012 - Current GMATPpre v1.1 2006 - 2012 GMATPrep v1 2005 - 2006 PowerPrep 1999 - 2005 (overlaps with OG) Collection of all SC questions from GMAT Prep (don't take these until you have exhausted all of the tests)

1. What is GMAT Prep and where to download GMAT Prep?:
GMATPrep is a GMAT Simulator software provided by GMAC (General Management Admissions Council) for free to help MBA applicants prepare to the test.
It can be downloaded from GMAC's official website (MBA.com) https://www.mba.com/mba/TheGMAT/DownloadFreeTestPreparationSoftware/

2. Why is GMATPrep valuable?
The value of GMAT prep is that it is able to predict one's GMAT score more accurately than any other product on the market.
The key lies in using real gmat questions and same testing algorithm as GMAT. Also GMAT Prep test has the same interface as the real GMAT test, so that the experience from taking the GMAT Prep is very similar to the one in the test centre . No other product is able to provide this value.


3. Getting the Most out of GMAT Prep
Now there is a number of different strategies on how to use GMAT Prep tests most effectively. And the answer to which one is the best, of course is — it depends.
Most people agree that its good to keep one test till the end of the preparation process to use it as an accurate estimator of the GMAT score.

Though some people recommend to take it more than two times... one or two extra times in order to get new questions. Some real fans even go to the extent of squeezing all the life out of it by taking the test until they don't see any new questions. It's up to you to decide whether this is a good strategy for you. But if you ever want to take GMAT Prep more then twice here is how to do it:

GMAT Prep "Reset" - Reinstall
1.Go to C:\Program Files\GMATPrep\Exams
2.Within the Exams folder, you should see a Practice Test 1.log and a Practice Test 2.log
3.Delete or I'd say move to other location both logs*
4.Relaunch the GMAT Prep software, and it should show you that both practice exams are now Not Attempted, and you can take them again.

GMAT Prep "Reset" - Reinstall in Windows Vista (Special thanks: to bigoyal for researching this)
1. Basically same as above only GMATPrep creates folder in following location:
C:\Users\{user_name}\AppData\Local\VirtualStore\Program Files\GMATPrep\exams
Note: {user_name} is your user name, it will vary from system to system
2. Usually you can go directly to AppData folder by typing in "%appdata" - in explorer window
3. Make sure explorer shows hidden files

Feedback from GMAT Club Members:
- Quant question pool is larger than verbal pool; if you take tests multiple times, the chances of seeing new question are higher for the Math section.
- Question pool for “hard” questions is fairly small and chances of seeing new questions when you get to 750+ score range is small.
- AWA questions are static and do not change

*To learn about GMATPrep Log files and how to read them, please see a post directly below


5. Want 2 more adaptive tests? Use PowerPrep
PowerPrep is the previous version of GMATPrep developed by ETS. This software product is no longer supported by GMAC and no longer distributed, but we have a copy. It uses the older GMAT interface and potentially an older GMAT algorithm. Here are a few considerations about using PowerPrep.
1.There seems to be no question overlap between GMAT Prep, and Powerprep
2.There is, however, a significant overlap between OG and Powerprep, so if you already worked on OG, your score might be significantly inflated
3.There are reports that PowerPrep isn't truly adaptive and not as good of an indicator of performance on the real GMAT.
Download GMAT PowerPrep


6. What Other GMAT Preparation Resources Are Available?
GMAT Club Tests
GMAT test reviews, pricing and links.
Top 20 Most referenced GMAT books


7. Issues with GMATPrep Software
Practice Test 2: Application error has occurred. The Application will exit now
How to reinstall GMATPrep