G'Day
With the first problem, it sounds like the uninstall script is corrupted so, reinstall comodo to exactly the same folder again. This will recreate the install script. Reboot (just in case a reboot is required to complete the installation) and then try to uninstall it again - check to see if there is an uninstall option first, if there is use that to uninstall otherwise use Add/Remove Programs.
Regarding the second question, there are several things to try (in order); for each program that auto starts with windows check to see if there is an option, usually in Options/Preferences, to Start with Windows (or similar wording), if there is untick/uncheck (or whatever is necessary) so that it no longer autostarts. Reboot and check that they no longer autostart.
If there is no option then click Start>Run and type in msconfig and hit enter or click OK. Then click the Startup tab and have a look at what is starting. Untick/uncheck those programs you do not want to autostart then click OK and accept any messages you get. Reboot and see if it is now quicker and all the programs you dont want to start automatically are not starting.
There are some programs that are notorious for installing themselves so that they autostart, Quicktime and Acrobat Reader are two that I can think of off the top of my head, and the msconfig method is the only way I have ever found that stops them autostarting.
If you find a program that you changed does need to autostart, then just reverse theprocess you used to stop it.
Geoff