This site gives you the names of almost all items that could be running in background, a description and whether they are needed or not and has a search engine.
Startup Applications List
Keys:
* "Y" - Normally leave to run at start-up
* "N" - Not required - typically infrequently used tasks that can be started manually if necessary
* "U" - User's choice - depends whether a user deems it necessary
* "X" - Definitely not required - typically viruses, spyware, adware and "resource hogs"
* "?" - Unknown
http://www.sysinfo.org/startuplist.phpgoogle startup list for more sites like this if you can't find it here.
On Edit
Startup cop is what I use to find out what programs running in background
you can get it here
http://www.pcmag.com/article2/0,4149,2173,00.aspDescription:
When Windows starts up, it automatically launches a number of programs for you. Some of these come from the Startup folder. Windows also looks in six other locations for files that should be launched at startup. Startup Cop helps you handle problems with programs that are automatically launched at startup by listing them and letting you disable, enable, or delete them. You can save the list of programs that are currently enabled or disabled as a profile that can be restored at a later time.