How can I remove GRUB2 from my iMac?

Question

Hello Internet!
I have a 21.5" iMac (intel based, version 10.7.5), and I have recently tried to install Ubuntu on it.
Ubuntu installed successfully, and with it came GRUB2. Now, when Ubuntu started doing all sorts of wierd crap i decided i might as well just use it from a LiveCD or LiveUSB and remove it from my system. So i deleted all the partitions (including SWAP).
I have managed to remove the SWAP partition which is parcticularily tricky, by erasing and reformatting it to a Mac OS Extended (Journaled) format, and then simply removing it from the disk utility.
Now, I have installed rEFIt, and when booting my computer I see two options in my rEFIt - on the left I see a "EFI/somethingsomething/grubfile" (not the real directoy, It just says GRUB in the end and it is in the EFI) and on the right I see Mac OS X. I wondered how can i possibly remove GRUB2 completely from my system?
Thanks for any help .

Answer 1

You have quite muddied up the waters, I'm afraid. Assuming you now have a single GUID partition formatted Mac OS Extended, Journaled, you should try reinstalling Lion:
Reinstalling Lion/Mountain Lion Without Erasing the Drive
Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.
When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list.  In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive.  If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the main menu.
Reinstall Lion/Mountain Lion: Select Reinstall Lion/Mountain Lion and click on the Continue button.
Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.