Have to test a c# application from client that is to work on a machine that has FIPS enbaled
First, be aware of what actually happens when you enforce FIPS140-2 complient encryption within Windows. Details are at http://technet.microsoft.com/en-us/library/cc750357.aspx. However, the main 'gotcha' (old SSL website's don't work in IE anymore) is detailed in the article linked below.
The official instructions to enable FIPS 140-2 complience are at http://support.microsoft.com/kb/811833, but can be summarised as follows:
If you wish to do this manually, you can also simply change the registry key HKLM\System\CurrentControlSet\Control\Lsa\FIPSAlgorithmPolicy\Enabled
to 1
Finally, to repeat, it is very important that you read through the documentation before you enable this - it changes cryptography system wide, including how the file system (both EFS and Bitlocker) and network (IE, Remote Desktop and the main cryptographic libraries) are allowed to encrypt, as well as if you allowed to recover lost encryption keys.