Most of the services are part of windows and cannot be
deleted (you could delete the files from the start path,
but windows might not work proberly after that)...but you
can disable services.
Open the services and highlight the one you don't want,
click on proberties and choose disable from the start typ.
Some non-windows services you've added later (like a video
card)can be deleted by removing the program from the
add/remove list.
