I'm running VMware Workstation 6.5* on Windows 7 Enterprise 64-bit. It works well but I keep getting the dreaded warning about the clock speed not matching. To fix this it's usually a matter of just updating the config.ini, as documented here.
Except that under Windows 7, you can't save the config.ini. In fact, you can't write to the C:\ProgramData folder at all. Not even if you change the owner of the folder to your account. So what do you do? You have to temporarily change the User Account Control settings to Never Notify.
Go to Start Menu -> Control Panel -> User Accounts and Family Safety -> User Accounts.
Select User Accounts
Select Change User Account Control Settings
Move the slider all the way to the bottom
Now restart your computer. Once it comes back up you should be able to edit the config.ini. After you are finished you should kick the UAC back up at least one notch.
* VMware Workstation 7 uses a different method for determining host CPU speed and does not need this manual adjustment.