If you have set the home page back in the browser settings, but it keeps reverting, most likely that is because some sort of browser add-on, toolbar, or some other software was installed and is setting it back. This is *really* easy to happen, as lots of inexpensive software installs this sort of thing in order to get a kick-back from Google (or Yahoo or MS). Typically the software will ask if you want to install this, but it is subtle and most people click right past it without noticing.
Go to Control Panel, Add/Remove Programs (or Uninstall Software) and see what is installed. Uninstall anything suspicious there. SOrry I can’t say which program it is for sure w/o seeing it. You might also go into Firefox Add-Ons and look at the browser extensions/add-ons to see if it is there. You can probably disable it from there as well.
Good luck.
This is the most likely problem.
Go into Uninstall/Remove Programs and remove anything with the name “toolbar” in it. Toolbar trash is never needed
and is just another way for google etc to get a foothold on your PC.