You can use the MyEclipse uninstaller to remove a MyEclipse installation and that is the preferred method. The Windows start menu, or equivalent in other systems, will usually have an entry for the uninstaller. Alternatively, it may be located in the folder named "Uninstaller" under the MyEclipse installation folder. The executable is called "one-uninstall". If that program fails, for some reason, use this manual uninstall method.
MyEclipse does not update or add any registry entries on Windows but it may add start menu items, depending on how it is installed.
So, to manually remove a MyEclipse installation, simply delete all the associated files and folders. Read this FAQ for details on the default locations of these files and folders:
Where are the MyEclipse files and folders?
If you changed the defaults then delete the folders that you specified during installation, plus the standard files and folders that are installed in your home directory, as indicated in the above FAQ.
If you installed into a classic eclipse distribution, using an update site, or archived update site, then use the standard eclipse uninstallation methods.
Don't forget to delete any start menu items or launchers that were created during install.
A quick way to uninstall is to look at the contents of the .deliverycenter.installs
file (in your home directory - see the FAQ on files and folders mentioned above) and delete the folder mentioned there, against the relevant release. For releases prior to 2013, you should check the .pulse2.locator file instead, which can also be deleted.