The following will implement preventative measures and will avoid an unusable Visual Studio 2010 on your brand new Windows 7 OS if upgrading from Windows Vista. Please note that .NET Framework 4 Beta 2 has resolved this issue.
If you upgrade to Windows 7 from Windows Vista with the .NET Framework 4 Beta 1 installed, your machine will be in an unreliable state. In this state, Visual Studio 2010, and some managed programs depending on .NET Framework 3.5 or earlier will not work. There is no way to repair a machine that gets into this state. You will need to reinstall Windows 7.
However, uninstalling .NET Framework 4 Beta 1 before upgrading to Windows 7 alleviates this issue and upgrading should work fine. Below are detailed steps to completely remove .NET Framework 4 Beta 1 as well as Visual Studio 2010 Beta 1.
Uninstalling Visual Studio 2010 Beta 1 and .NET Framework 4 Beta 1
Perform the following steps to completely remove Visual Studio 2010 Beta 1 and the .NET Framework 4 Beta 1 from your machine.
1. Uninstall TFS Object Model (Visual Studio Team System 2010 Team Suite Beta 1 customers only)
a. Click Run from the Start Menu (or press Win+R)
b. In the Run Dialog box, type control appwiz.cpl and then click OK.
c. In the list of installed applications, select Microsoft Team Foundation Server 2010 Beta 1 Object Model and then choose Uninstall
2. Uninstall Visual Studio 2010 Beta 1
c. In the list of installed applications, select an instance of Visual Studio 2010 Beta 1 (e.g. Microsoft Visual Studio Team System 2010 Team Suite Beta 1) and then choose Uninstall
d. The Wizard will load then on the Welcome screen click Next to proceed.
e. On the Maintenance page click Uninstall and choose OK to completely uninstall.
f. The Uninstall progress dialog will show the progress and then you should see the finish dialog indicating whether the uninstall was successful.
g. Reboot if prompted.
h. Repeat this step 2 for each installed version of Visual Studio 2010 Beta 1.
3. Uninstall .NET Framework 4 Beta 1
c. In the list of installed applications, locate the following applications and choose Uninstall for each in this order:
i. Microsoft .NET Framework 4 Extended Beta 1 - Language Pack
ii. Microsoft .NET Framework 4 Client Profile Beta 1 - Language Pack
iii. Microsoft .NET Framework 4 Extended Beta 1
iv. Microsoft .NET Framework 4 Client Profile Beta 1
4. Uninstall C++ 2010 Redistributable
c. In the list of installed applications, select Microsoft Visual C++ 2010 Beta 1 Redistributable (x86 and/or x64) and then choose Uninstall
6. It is now safe to start upgrading to Windows 7