Recommended for advanced users:

You might wish to delete a service at some stage, perhaps one that remains after an uninstall (I've even seen a service remain in W7 after a system restore to a point prior to the installation!)

Go to your Registry Editor (windows+R and then type regedit > enter.)
Select HKEY_LOCAL_MACHINE > System > CurrentControlSet
Select Services folder
Examine the listed services (they're in alphabetical order)
Highlight/ select the service you wish to delete > right click > d...

{The easiest method is to do a system restore to a time before the installation but as you're here you probably cannot do that}
 
Should you wish to delete ICQ, first go to add/remove programs (where you'll need to delete both the toolbar and the application)
Restart Firefox and, should ICQ still remain:

Open a fresh Firefox tab, In the URL address bar type "about:config" (not the quote marks) > notice the warning message > do be careful
In the "Filter" box type : "keyword.URL" (without quotatio...