First, update your computer to Service Pack 3.

Then, scan for viruses. Troubleshoot Firefox issues caused by malware

Then, download Firefox from www.getfirefox.com and install it (don't remove Firefox first)

If you are using any registry cleaners or the like immediately uninstall them.

but I can not update my comp or download anything because no one of Web browsers doesnt works.

Then something is majorly wrong with your machine. Take it to a local, reputable computer repair shop, tell them you want to use Firefox but none of the browsers on your computer work. They should fix the machine, updated it, remove any viruses and you should be good to go.

Yeah, but there is inly one problem: That I want to save my many.

Well we can't really help you here. You can try downloading the tools I gave you a link to on a another computer and put them on a USB drive, but diagnosing a whole computer problem is beyond the scope of this site.

then reinstall windows xp from scratch http://lifehacker.com/157578/geek-to-live--how-to-format-your-hard-drive-and-install-windows-xp-from-scratch http://www.wikihow.com/Reinstall-Windows-XP

Thanks anyway. I still think that Firefox caused problem that other browsers won't works.

Firefox can't cause a problem to keep other browsers from working, so that's not possible.

Do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

• C:\Program Files\Mozilla Firefox\
• http://kb.mozillazine.org/Installation_directory

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 18.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored in the Firefox Profile Folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

If you keep having problems then also create a new profile.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

Seems a bit of default solution for "couldn't load XPCOM" - uninstalling FF.

For me ZoneAlarm Security was the problem.

Open Task Manager. Do a Ctrl + Alt + Del and open Task Manager. Select ZoneAlarm Force Field and click End Task.

If Firefox now works here is how to cure the problem.

Open ZoneAlarm. In the Internet box click on View Details. Turn off Web Security. This will cause a Fix it button to appear. Click on the Fix it button. Web security will be set back to on and Browser Virtualization will be turned off. Turn on Brower Virtualization. Close ZoneAlarm.

Firefox should now work.