I have Excel versions 10 and 11 on my machine - installed in separate
folders. Excel v11 suddenly began taking an extra 15 seconds when
starting up. I found fhe file "Excel10.xlb" (documents and
settings/.../microsoft/excel) that seemed abnormally large (200kb), so
I renamed it. Now Excel v11 starts normally again.

Question is: how does that file from version 10 have anything to do
with starting Excel version 11?