Microsoft released a Community Technology Preview of Visual Studio 2010 and .NET Framework 4.0. The CTP, released as a virtual hard disk image designed to integrate with Virtual PC 2007 SP1, is set to expire at the start of 2009. However, testers have the possibility to prolong the CTP's life beyond the expiration period with Microsoft's blessing, in order to keep on running the pre-release build of Visual Studio 2010 and .NET Framework 4.0, until the next updates will be offered.
So you’ll want to make sure that you don’t use the VPC and then set the clock backwards after that point. Ideally, you can use a fresh VPC and disable your clock prior to launching it for the first time, Jeff Beehler. Ben Armstrong, a program manager on the core virtualization team at Microsoft, details the necessary steps available for disabling time synchronization under Virtual PC 2007.
After January 1, 2009, you will no longer be able to launch the Visual Studio 2010 CTP. This is due to a hard-coded expiration date in this CTP. CTP's are pre-release software, so they aren't designed to run forever, Brian Keller. “Note that you should not roll back your system clock to a date prior to your last interaction with Team Foundation Server, because otherwise Team Foundation Server will get confused. If possible, I would suggest rolling back to a clean copy of the VPC (uncompress the original) and immediately disabling your clock prior to launching it for the first time.”