There are many small apps that turn off the start button,startkiller is one by tordex.com.U have to install this one,but there are others that do it on the fly.Of course u will need to deactivate ur sfc so windows doesn't put it back after a restart,but startkiller program might deal with that since u install it.
I haven't tried this one by the way,but it says it works on win7.I just googled "turn off start button windows 7" and this was one of the first few that came up.I'm sure if u look about more there might be a reg entry or something easy u can do.I've done my bit anyway.