In Ireland can you call HMV to reserve DVD's (or Blu-Rays etc)?

OK, I'm only 12 years old so sorry if I sound kinda stupid cos I don't know this stuff and I need an answer quick cos Harry Potter and the Deathly Hallows Part 1 came out on DVD (and Blu-Ray)yesterday and I'm going to my local HMV tomorrow and I REALLY want to get it but I'm afraid that it might be sold out so can someone tell me if your actually able to call a DVD (or Blu-Ray) store to reserve it or would it not be very likely for them to be sold out anyway? Please answer quick if you can and again sorry if I sound stupid but I'm just a really dumbass 12-year-old.