Today I Learned that Acrobat Reader has a hook in Windows Explorer to pre-cache PDF files found in the current directory.  This would be fine if (and ONLY if) I were on a machine that had rapid disk access or excellent file handing.  I am not, and my system does not.  So every time I see AcroRd32.exe show up in my task manager – every time I open up a directory with PDFs, basically – I get about 10 seconds of busy cursor.  Distracting, annoying, unnecessary.