There are a number of ways that unwanted software could modify your home page. The most common are:

• Directly changing the setting, although you usually can fix this with a one-time change on the Options page (Startup, home page, tabs, and download settings)
• Installing an extension in Firefox (add-ons may change your home page at startup only, or may keep overriding your changes any time you make it)
• Creating a user.js file (overrides your normal settings at every startup; removed by a Refresh)

Extensions can be installed either in a particular profile folder -- in which case a Refresh will remove them to the Old Firefox Data folder on the desktop where they will no longer bother you -- or externally. External extensions usually are advertised in the Windows registry for Firefox to find.

If your post-Refresh Firefox has not reinstalled any bad extensions, you may be clean now. Just in case, you can view a compact list of your extensions on the support information page. Either:

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

Scroll down to the Extensions heading and a table should follow showing all the installed extensions and whether they are enabled. Anything suspicious? If you like, you can select the heading and table and copy (Ctrl+c) then paste (Ctrl+v) into a reply here to get a second opinion.

Finally, to address the protection question, each security product has a different threshold for when annoying software is considered a threat to be removed. If you want to use some supplemental scanners, check out the list in our support article: Troubleshoot Firefox issues caused by malware.

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.