It's a gray mountain bike frame that says Giant on it and the serial number is GE481578.
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I've looked through a few models for various years at http://www.bikepedia.com/QuickBike/Bikes.aspx?year=2004&Brand=Giant
The chainstays on yours don't get narrower towards the rear, suggesting lower-end, but it's not a Boulder, because I can't find a Boulder with a downtube gusset. Disc-only points towards late 2000s mid-range.
Giant's graphics switched from outlined text to block text for the 2007 model year. Many models also switched from downtube gussets to hydroformed downtubes in 2007.
I don't think this is the original paintjob, as I can't find a model with both block text and a downtube gusset. Also, black branding on such a dark colourway doesn't seem like a catalogue option.
My best guess is circa 2006 Rainier, Yukon or Rincon. Extremely unlikely to be an XTC, since those have XTC instead of Giant on the downtube.