We had an instance of SQL Server 7 running on a Windows NT box for 10 years without a reboot. Granted, the server did not do much heavy lifting. We never had a Windows 2000 or newer server that has not had to be taken down at least once though. We eventually took down the NT box when we revamped the reporting system and it was no longer needed. Had we not done that, it might still be running today. I agree with Steve, for us Windows has required more maintenance than SQL Server due to the patches. The longest we have had a SQL 2000 server run without maintenance was 3 or 4 years. But that was on a Windows 2000 server. It seems our Windows 2003 and Windows 2008 boxes have required more updates.