Any free Performance testing tool for Desktop applications for 50+ users.

HP Loadrunner is the baseline tool for any performance engineering, it can be used for monitoring, tuning, analysis of performance test runs. 

You get 50 Vusers as license free from HP team from HP Loadrunner version 12.01. Beyond the 50 Vusers you need to pay for the license costs. Apart from this tool, I am not sure which other performance tool supports desktop application performance testing (This performance tool supports many technologies and also you can script in VB, C & Java), supports many protocols. 

HP Loadrunner is a commercial tool.

i want to learn performance testing.So please can any one suggest me which tool is better either?

It is very important to understand the concept of Performance Testing like -What is Performance Testing, Why do we automate Performance, Understanding the server -client architecture. After,that you can move to tool like Silk Performer, Jmeter or Load runner.

Learning tool is not so difficult but understanding the concept of performance testing and its requirement is the most imp part as every time while working on tool or as a performance tester you will require the concepts.
All the tools are same in means of recording, execution, No of Virtual users, parameterization, correlation etc but the look and feel is different of each tool.

Now Talking about tools
Jmeter
If you are just learning, I'd go with Jmeter since it is free. Once you have the basic principles of Performance Testing down, then maybe look into other


Borland Silk Performer
It delivers realistic, dependable performance tests across the latest technologies by simulating loads and network speeds for web, enterprise, and mobile applications.
http://www.borland.com/products/silkperformer/

HP Loadrunner
This will give you some of the basics for how to record and correlate your application. There are lots of detailed manuals and online help.

Grinder
The Grinder is a JavaTM load testing framework that makes it easy to run a distributed test using many load injector machines. It is freely available under a BSD-style open-source license.

NeoLoad
NeoLoad is a load and performance testing software solution designed for web and mobile applications, which realistically simulates large numbers of users and analyzes your server behavior.

http://www.neotys.com/performance-load-testing-tools.html

But I recommend that use silk performer first for better understanding then use Loadrunner and then Jmeter.

Setting for WAN test in silk performer and Load runner

Bandwidth –
In networking, bandwidth is the maximum channel capacity of a network communication path. This path is the channel connecting computing devices. In performance tests, when aspiration is to emulate test more close to real time situation, bandwidth restrictions are also taken into consideration. Modern performance test tools provide us with the feature of putting network / bandwidth related restrictions. In loadrunner, this can be done using ‘speed simulation in ‘run time settings’. In SilkPerformer, this can be done by changing ‘Internet settings’ in ‘Active profile settings’.

SilkPerformer Network Settings -

Step 1:-

Open your project and Go to the Profile

Step 2:-

Once you open your profile,On left side you can see Replay Tab,Click on that Tab

Step 3:-

Thinktime here in pics. is only for representation purpose, you can choose thinktime according to your requirement.

It's better to Select three option shown in pics.(It's upto you)

Choose thinktime in ThinkTime Box, Checked mark three option showing in the above pics.  

Step 4:- 

Truelog files should be enable for bandwidth test.If you enable Truelog files option then Truelogs file will generate,Otherwise truelogs files will not generate.

Go to Results and enable TrueLog Files

Step 5:-

Customize your bandwidth for which you want to perform bandwidth test as shown below pics.

Go to Internet, choose Custom-Bandwidth and Select your bandwidth speed

Step 6:-

Simulation we choose as REVISITING because from that we can get both types of response time i.e
Response time without caching and Response time with caching(But for that you have to make script as multiple login logout and Iteration make it as 3(Tmain - 3) )

Choose Simulation as Revisiting

LoadRunner Network Bandwidth Settings -

Step 1:-

Step 2 :-

 Step 3 :-

Bandwidth simulation can be achieved more effectively by using WAN emulators.
WAN emulation –
WAN emulation is creating a network scenario in the test environment, exactly similar to production environment (real-time, end user scenario). This can be achieved using WAN emulation tools. Popular amongst those are – WANem, Shunra, etc.
WAN emulation thus allows the performance test team to setup a transparent application gateway which can be used to simulate WAN characteristics like Network delay, Packet loss, Packet corruption, Disconnections, Packet re-ordering, Jitter, etc.