task manager will tell you.
right click the task bar/task manager/performance
applications tab for programs running
processes for services etc
to stop programs stsrting up with windows click:
start/run and type "msconfig" and click ok.
click the start up tab and untick all except your AV and firewall.
for reference to what you are stopping loading at start up click here and look them up
you can disable services that are not needed too click here go by the "safe" setting and you should have little problems.do one or two at a time and restart the computer to check all is well.
set a restore point before any of the above just in case,i have had no problems following the guides from these sites.