Sometimes I need to configure a test Windows virtual machine and use it for only for a week or two. Well if you are using a Microsoft Windows Server 2008 R2 OS like me and you have only 3 days till activation then continue in reading this post:)
There are two things to configure and they are not so complicated.
1) Disable automatic activation with the use of registry editor like in the picture below.
Visit this path in the registry editor (Run>regedit): HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SoftwareProtectionPlatform\Activation. Edit or create a DWORD “Manual” value with a value data of 1.
2) Now reset the evaluation period by entering slmgr.vbs -rearm in the command prompt (Run As Administrator).
After that you will be asked (forced) to restart your computer. For the elaborate story on slmgr.vbs visit Microsoft suporrt –> http://support.microsoft.com/kb/948472
Hope it helps!