How do I know what addons I have installed. I want to remove some but I don't know how many there are and stuff.

Your so-called "addons", are simply loaded scripts, you can view all the scripts loaded via, ALT + R - Click 'View Menu'. they are listed there.

You can unload them by selecting them from the above menu and clicking File + Unload.

Note; That if there are several "features" scripted in any one file (i.e. Not 1 feature to 1 file) then unloading one file will result in them all being turned off (not lost they are still able to be reloaded via, File + Load.

If there are infact multiple features in any one file, you will need to actually know scripting and locate the parts you wish to disable and place a ; before each line which will automatically stop it working.

Eamonn.