I have a client with roughly 700 Windows servers (some 2000, mostly 2003 and 2008) in various stages of patching. Their servers are a typical mix running Exchange, Domain Controllers, SQL clusters, IIS, SCCM, ISA, Symantec NetBackup, and IBM FileNet.
Some servers haven't been patched in over 3 years.
Does anyone have any experience as to what the best way of going about this is?
Install service packs, then patches.
Get the servers to the latest SP level first and you will save a lot of time on the patches after that.