how can I disconnect the alarm

I would ask a BMW dealer, there is a process to shut it off.

if you want the alarm disconnected you need to take it to a dealer so they can retrofit it out. its not a do it your self job

cut the blue wire

who told you its in the glove box that guy is a douche.... what you need to do its climb under the steering wheel, your going to see a a rectangle shape black box multipule connectors in there.. you can't miss it.. on the biggest connector there is a red wire, cut that wire.. stripp it back.. then on the smallest conector there is a black wire or maybe a yellow wire depending on the unit.. cut that wire and strip it back and join the two wires with a butt conector or better yet soilder.. that will pypass the alram.. real easy to do ten minutes if that.. your friend from buds bmw...

i agree with larry. its the blue wire, but make sure you tape off the ends, you dont want to short anything out. and if i recall correctly, the wiring harness is behind the glovebox.

We're not stealing a 540i are we?

there is also a simple fuse you can pull in the trunk. just pull open the cover that is over the battery. and look for the fuse labeled alarm! its that simple.