There is also other items to consider when looking at loading SP4 on several hundred machines. Mainly, if you write a script to automate the process, be careful on how you answer any questions the SP gives you. We just finished running the SP on a couple thousand PCs using a script to automate most of them. Well, when we wrote the script we didn't think that it would overwrite vendor modified files and cause problems. It did. Nt often enough to halt everything, but enough were a couple people were always recovering BSODs. Just use some care and remember the more variety in PCs, the more likely you'll see some problems.