on where you purchased the iMac.
If you purchased it in the Europe/UK area, then Yes, it will definitely play it.
If you purchased it elsewhere you are still in with a chance.
Apple allows up to 5 region changes for your Optical drive. It comes set for the country/region that you purchased the computer.
When you insert a DVD from another region, the system will ask if you want to change to the region of the DVD and will tell you how many changes you have left. Once you reach the last change, that's all she wrote and you will be stuck at the last setting.
Does that help?
Before buying a region 2 (europe, uk) dvd and just winging it I thought I'd ask the forum if this dvd player in the slot in my 24" intel i-mac running leopard will play region 2 dvds.
Here is the specs from 'about this mac' about my dvd player: MATSHITA DVD-R UJ-875:
Firmware Revision: DB09
Burn Support: Yes (Apple Shipping Drive)
Cache: 2048 KB
Reads DVD: Yes
CD-Write: -R, -RW
DVD-Write: -R, -R DL, -RW, +R, +R DL, +RW
Write Strategies: CD-TAO, CD-SAO, DVD-DAO
Media: Insert media and refresh to show available burn speeds