There have been lots of questions about how to carry out upgrades from/to various versions and in general the response has been to install the new version beside the old and backup/restore the database from one instance to the other. This is what I have done and have met no real issues in that. I am now ready to remove the old versions. Is this simply a case of uninstalling the old version (SQL 2005 in my case) or are there 'gotchas' that I need to consider? Are there any risks of shared dlls being removed and causing SQL 2008 problems? Does it require a reboot? What experiences have you had that I might have to look out for? TIA
Have you got a compelling reason to remove it aside from neatness? A service that's installed but not running will only take up disk space - so unless you're short on that... ? Basically I wouldn't like to say 'no it will be fine' because I'm sure there would be some DLL somewhere that would cause an issue. I remember trying to install / uninstall various versions on a dev box gave us quite a lot of grief (after uninstall of one, the management tools for the other wouldn't load) - but I have a feeling that was a fight between 2000 and 2005, rather than 2005 and 2008.
Also, if you're doing more migrations in the future, the best method is not to install the service on the same machine, side-by-side, but rather to install the service to a new machine and then migrate everything over. This is used for two reasons, one, the uninstall that you're running into could actually cause problems, so is best avoided, two, if there is a problem during the install or the migration, your original system is completely unaffected so that you can instantly recover it. This will help going forward. For where you are now, I'd take Matt's advice.