If you are an Advanced User who has priviledges to edit Registry here you go.
Method 1:
Close Visual Studio (if its open)
Start > Run > RegEdit
(Backup registry before making changes)
GOTO
HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\<version>\ProjectMRUList
remove unnecessary items from list.
If needed reorder your list. File1, File2 etc. Otherwise Visual Studio might not read them properly.
Similarly repeat the steps for FileMRuList
Method 2:
If you can’t edit registry or not feeling comfortable here is an alternate method.
http://www.codeproject.com/csharp/VSRecentcleaner.asp
Happy Programming
I wrote a powershell script for this. Here is my post on it.
http://techsoda.wordpress.com/2007/08/24/powershell-to-clear-out-visual-studio-mru-list/