Narahari,
Run the uninstaller, if there is one (under the Ubuntu Applications->Programming menu). Otherwise, just delete (rm -rf) the directory in which MyEclipse was installed. That directory will have a Common folder and the specific MyEclipse version folder; just delete the parent folder.
If you want to completely eradicate MyEclipse then you’ll also need to delete the .myeclipse folder from your home directory, along with any files named .myeclipse* or .pulse2*. That should do it.
If you’re installing the 64 bit version, then don’t forget to make a note of your subscription ID and code, though you could just leave the .myeclipse.properties file, in your home folder, and the subscription info will be picked up from that.
You’ll need a 64 bit JRE, to install the 64 bit MyEclipse.