You MUST visit  the official uninstall instructions found at the Express download site before following the following hack. 

Issue: When Visual Studio Express 2005 Beta products are uninstalled in the order different than the post at http://lab.msdn.microsoft.com/express/uninstall/  For example, .NET Framework was uninstalled before Visual Studio client was uninstalled. The machine is left in a dirty state and future installations of Visual Studio and the .NET Framework may be affected. This is not a Microsoft supported scenario.

.NET Framework needs to be uninstall last. Users can try to install back the Framework before retrying the uninstall of other components in the RIGHT order specified here.

If that also fails, You cant try to perform the following steps to manually clean up the Framework and Visual Studio on the machine. However, this doesn't clean up the other components installed by Visual Studio Express, such as SQL Express, SQL native client, SQL supporting tool etc. If the previous version of these components are not removed, the future install of Express would fail for these components.

 

Notes: Before proceeding please note these important caveats:

·         These steps do not work for the version of the .NET Framework that is installed as part of non-released OS

·         As long as you intend to install a later build of the .NET Framework 2.0, previously shipped versions of the .NET Framework (1.0 and 1.1) will continue to function properly after performing all of these steps. However, these steps should not be used to manually uninstall and clean up the .NET Framework 2.0 in side-by-side scenarios. If you only intend to use these steps to manually uninstall the .NET Framework 2.0, you must repair the .NET Framework 1.0 and/or 1.1 after manually uninstalling 2.0.  The steps required to repair the .NET Framework 1.0 and 1.1 can be found by locating the .NET Framework 1.0 or 1.1 entry in the Add or Remove Programs Control Panel, clicking the link to view support information and clicking the Readme link in the support information dialog.

 

Steps to clean up Framework on a machine

·                     Using regedit, navigate to HKLM\Software\Microsoft\.NETFramework and delete any keys and values that have 1.2 or 2.0 in it, including keys/values that are in subkeys underneath .NETFramework.

·                     Using regedit, navigate to the sub-hive HKLM\Software\Microsoft\.NETFramework\Policy and delete any key or value that has 1.2 or 2.0 in it.

·                     Using regedit, navigate to HKLM\Software\Microsoft\ASP.NET and delete any key or value that has 1.2 or 2.0 in it, including keys/values that are in subkeys underneath ASP.NET.

·                     Right-click on My Computer and choose Manage. Expand Computer Management (Local), then Local Users and Groups, then click on the Users folder. In the right-hand pane, right-click on the ASPNET user account and choose Delete to remove it.

·                     Go to %windir%\assembly and delete anything with *1.2* or *2.0* in the folder name. Delete the GAC_32 and GAC_MSIL folders as well. Note: You may need to set the registry key at

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion]

"DisableCacheViewer"=dword:00000001

in order to be able to view the sub-folders in %windir%\assembly using Windows Explorer. Delete the DisableCacheViewer after completing this step

·                     Go to %windir%\Microsoft.NET\Framework and delete any folders named v1.2.* or v2.0.* along with all of the files and subfolders they contain.

·                     Rename %windir%\system32\mscoree.dll to mscoree.dll.old.

·                     After doing all of this, try to install the previously failing build of the .NET Framework.

 

Steps to clean up the VS client on a machine

Issue: This application has failed to start because the application configuration is incorrect

 

Summary: When the user machine used to have old versions of VS 2005 (e.g Beta1 or CTP), installing a newer version sometimes cause the above error dialog when users launch the IDE. This is caused by old WinSxS assemblies left over in %windir%\WinSxS folder.

 

Cause:
When the user machine used to have old versions of Whidbey, installing a newer version sometimes cause the above error dialog when users launch the IDE. This is caused by old WinSxS assemblies left over in %windir%\WinSxS folder.

 

Resolution:
Steps to resolve the problem is:

·                     Go to the System event log and look for error logs with event source "SideBySide".

·                     Get the name of assemblies mentioned in the event log.

·                     Go to %windir%\WinSxS and rename the folders with similar names (for example *.VC80.*)

Launch Setup again, and choose to repair the product.

Thanks to Aaron for providing the contents, please refer to his blogs for more details.

Cleaning up .NET 2.0 - http://blogs.msdn.com/astebner/archive/2005/04/16/408856.aspx

VS issues (uninstall ordering and WinSxS assemblies) - http://blogs.msdn.com/astebner/archive/2005/04/16/408860.aspx