As you know, it bugs me when people blame everything on viruses when it's just a feature or goofy Outlook behavior, but it bugs me even more when the first step when troubleshooting is to uninstall and reinstall Office. Sorry folks, it's a huge waste of time and rarely fixes most problems. This is because uninstall doesn't remove or replace many of the registry settings or custom files Outlook uses.
Troubleshooting step 1 is load Outlook in safe mode. (Add /safe to the end of the command line in any Outlook shortcut or at Start menu, Run command, type Outlook.exe /safe).
If it works, then either an add-in, a config file, or your profile is the problem and you can disable addins or create a new profile to help identify the cause. If it still doesn't work, it's either the message store or an Outlook program file. Use detect and repair (or rerun setup for older versions) to replace bad program files, the effect is the same as uninstalling and reinstalling but much faster.
Step 2 is try a new profile. Don't copy the existing one and don't delete it, make a new one. If you have several email accounts, add just one to the profile to see if Outlook works right. (Outlook 98/2000 in IMO mode only allow one profile, so you'll have to replace it.)
For more troubleshooting tips, see:
Published June 21, 2005. Last updated on October 23, 2020.