I use my machine for development and research as well as teaching. Originally I only installed VS2005 and SQL Express. I later installed VS 2008. Finally I installed BizTalk (which required a full-blown SQL Server install) and thought nothing more of it.
More recently I was checking into how LINQ to SQL was doing some things and realised I couldn't find SQL Server Profiler on my machine - in fact I couldn't find any of the SQL Server tools! I googled this a bit and found this was a well known issue with installing SQL Express before SQL Server. So I resigned myself to sorting this out on the next repave.
I was talking to Kev Jones about this issue at DevWeek last week and yesterday he pops up and tells me he's solved it. Kev had the cunning idea of actually reading the SQL Server installation warning messages - which apparently tell you exactly what to do.
You can read Kev's post about it here