Is it possible to install/upgrade a HDD on 360 like it is on PS3?

Only if it is an Xbox 360 HDD, not like a PS3.

Yeah, you can even buy the 120gb and make it an elite...

So you have to buy an HDD for 360 specifically? Regular laptop HDD won't work?

I'm thinking about getting a 360, mainly because I already have the other two systems, but my collection feels...incomplete without a 360.

I reckon you could open up that 360 case and install a laptop hard drive in there. It's gotta be possible.

don't take my word for it though...

You can......

A) Use the actual Xbox 360 HDDs that just snap in.
B) Use a USB HDD


Those are your 2 options. If you use a USB HDD, I am not sure if there are any restrictions on it.

You can pick up a 20gb HDD, or a 120gb HDD. Try getting 'em second hand, you save a few quid doing so.

And, yeah, any USB HDD/Your iPod will work fine

Bearing in mind that you get a 256mb memory stick with an Arcade (only works for game saves, and storing offline profiles - you need an HDD for LIVE).

@omgwtfbbq
You can open the case and install a HDD, but it has to be a Western Digital BEVS Sata 20 or 120 Gig and you need to use The Specialists HDD security sector extractor/writer to extract the key from an already working HDD and write it to the new one. Bearing in mind that if Live sees 2 HDDs with the same key both consoles get banned.
@mrstickball
You can plug in a USB HDD but not save things to it, ony to stream music, pictures and movies.

You can only use a USB hard drive for streaming pictures, movies, etc.