my vectra?

hii , i have bought a vectra elite 2 weeks ago, 2002 model and it has got zenon lights , tv , dvd and everything . i didnot start the car for 4 days and when i tried yesterdaye it didnot start . i called AA and they said the battery ran out . they started the car and it was working fine . i drove the car for 30 mins and came bak home . todaye after 2 days i tried to start it again , it didnot start . i thought the battery gone bad , i went to halford and bought a new battery and still it did not work . i called AA todaye and they said somewhere the battery is running out and this is causing the problem . now , i do not know wat to do . can u please suggest me the possible solution ??? the car was working fine when i first purchased it . now am having all this problem . please advice me . i also went to a mechanic , he cant predict the problem . the AA mechanics saying dere is som sort of electrical problem goin where the battery drains out quickly . i need some proper suggestions . thanx