Been running Windows 7 (64 bit) release version for past week or so. Works a treat, runs well, doesn't have the occasional freeze that was plaguing my Vista install.
Just went to install Office Accounting 2009 before the bookkeeper arrives tomorrow and it went away with the fairies during the SQL install. Wouldn't end task for quite a while and took several prompts before restarting. Retried using the standalone SQL Express 2005 installer, but same problem - it went to scan the computer for something and didn't come back.
Had to uninstall the SQL components from the programs list in Control Panel. Then did a reboot for good measure. When it came back I did a manual install of SQL Express 2005 (64 bit). This worked straight off. Then I reran the Office Accounting 2009 installer and it worked :-)
Also tried running MSOA 2009 installer as Administrator.
Don't forget to add MSOA 2009 SP1. There are spearate US and UK versions, see here