THUNDERBIRD2 DOWNLOAD

I probably shouldn’t be posting this here, but this is the single best source of help for me. I downloaded Thunderbird2 and now have problems with my SENT folder, meaning no copies of my message being present. I downloaded it from one of two official sites through Internet Explorer. My question is will I have some sort of horrible crash if I downloaded it again over the previous one, hoping that any missing components or files will be “filled” in? Any Thunderbird experts out there! Thanks.