Hi, If you don't have Shockwave Flash Object Installed in IE, then that is why Flash Player is not working and why you see a red x at the Adobe test site.
Regarding FF, did you use the Flash Player Installer for FF?
Also when you disabled McAfee and then after Uninstalling FP and before running the FP Installer for IE, did you check to make sure McAfee was still disabled? If not, then perhaps McAfee blocked the Install of the Shockwave Flash Object.
Before trying to Uninstall/Install again, I would go to www.malwarebytes.org and download to your Desktop the Free Version.
Then I would Update it. Next Disable McAfee. Close all browser windows,then run a Scan with MBAM(malwarebytes) If anything is found, follow the instructions to remove it. MBAM finds malware that other programs can't. Once the Scan is completed, then re-enable McAfee.
Let me know on the Scan results.
Also did you use the Administrator Account?
One additional question: what files do you have in C:\Windows\syswow64\Macromed\Flash ?