Almost certainly un-needed programs starting with Windows. These can include programs that came pre-installed, such as Adobe Reader.
GG above mentions to type sysconfig into the run box; pretty sure that should be "msconfig" (without the quotes). Run it, select the start up tab, and have a look at what is listed. You might find the number of installed programs that decide they should start with Windows interesting.
How deep do you want to get into this?