Well first, you don't want to install Firefox 6, for several reasons: It has lots of known security holes ([https://www.mozilla.org/security/known-vulnerabilities/firefox.html https://www.mozilla.org/security/known-vulnerabilities/firefox.html]). There are plenty of performance and stability improvements in later versions that 6 doesn't benefit from. It is no longer supported. So, let's try this and see if we can't get you up and running. Go to [http://www.getfirefox.com www.getfirefox.com]. Click the "Download Now" button. Then instead of clicking run, Click Save. Save Firefox to your desktop. After the download is finished, go to your desktop, and double-click the installer. It should run, and Firefox should be successfully installed You can read [[Installing Firefox on Windows|Installing Firefox on Windows]], which has more information. a few other good things you can do to ensure your computer runs smoothly is Run all Windows Updates, install all needed service packs, etc. Update your graphics driver (Firefox uses your graphics card for some rendering, and an out of date graphics card driver can cause problems. [https://support.mozilla.org/en-US/kb/how-do-i-upgrade-my-graphics-drivers https://support.mozilla.org/en-US/kb/how-do-i-upgrade-my-graphics-drivers]. Update all your plugins (Flash, Java, etc.): [http://www.mozilla.org/plugincheck/ http://www.mozilla.org/plugincheck/]. Download and Install MalwareBytes Anti-Malware, run a full Scan. [http://www.malwarebytes.org/ http://www.malwarebytes.org/]. This helps check that there are no viruses on your computer causing issues. You can uninstall this program after you clean off any infections.