Thunderbird uses the browser marked as default in your operating system. Make Firefox your default browser instead of Chrome.

re 'had Microsoft take over my computer '

I've never heard of Microsoft doing what you claim, but I have heard of people with microsoft accreditation or claiming they are microsoft when they are not actual microsoft doing this.

One company rang my father claiming they were Microsoft, told him his computer was slow and had viruses. They asked him to enter a code and took over control to clean up the computer and then wanted him to go to a particular page and pay for the service. He did not ask them for help, they contacted him, so be wary of any similar bogus calls. He did not have any visus's either. They simply were trying to extract money, but as we had no idea what else they did, we changed all of his passwords and ran a virus check.

When someone has access to your computer they could see all sorts of info, like stored passwords. So, my advise is do not use anyone you do not know.

Close any opened Browser. You need to set up what browser you want as default. Start > Control Settings > Default Programs > Set Default Programs click on 'Firefox' click on 'Set this program as default'

check: Start > Control Settings > Default Programs > Set Program Access & computer defaults Select 'custom' and click on the downwards poiting arrow on the right side select: 'Mozilla Firefox' and put a tick in the 'Enable access to this program'

If you had Firefox open at the time: Select 'Use my current Web browser' and next to 'Mozilla Firefox' and put a tick in the 'Enable access to this program' Click on OK

Close Thunderbird. Open Firefox: Tools > options > Advanced > General tab at the bottom, select the option for Firefox to always check it is the default browser and click on OK. Close Firefox.

Open Thunderbird and check a link opens in Firefox.