From a previous contributor.
Windows Add/Remove uses the application's own uninstaller if one is available, so there's nothing wrong with heading directly for that immediately.
All ways leave much behind, and I always clear out everything afterwards with Find and Regedit Find, which it's perfectly safe to do. I've cleared literally hundreds of programs in this way and never once experienced a problem. Always remember that Windows keeps five days of registry backups in store anyway.
So called Registry cleaners like Regcleaner etc are also useless in this respect, since they ALL without exception fail to even recognise that these leftovers are in the registry.
Here's a general guide to clearing out the "bits". The following includes safety procedures. First carry out any available backup procedures that you have available. With Windows ME or XP, create a Restore Point.
Click Find, Files and Folders, type the application name into the dialogue box and press Enter. Then from the list found, make sure of the identity of each item individually and delete any components found to the recycle bin so you can recover from there in the event of any trouble. If the item you're looking for has a double name, put a question mark in place of the space, for example Hewlett?Packard. This will restrict the items found mainly to those relevant.
Then click Start,Run,type: regedit , and press Enter. Click Registry, Export, select All, and save a registry copy to the desktop as a safeguard.
Then, still in the Registry Editor click Edit,Find. Enter the application name in the dialogue box and click Find. There is no need for the question mark with double names in registry find. With any element found highlighted, press Del on your keyboard to delete it. Then press F3 to find next, and if anything is found, repeat the delete/F3 sequence until all references are gone. Then exit regedit. Together with the deletions in Find, this should clear out most of the components from your computer.
In the unlikely event of any registry trouble, right click the desktop registry backup that you made and select Merge. It will merge back into the registry undoing your changes. Otherwise, when you are certain all is well, you can delete the registry desktop backup.