Concealing a bow and arrow set:Is it possible?

[Masakan]

Put the stuff in a HHH, or BoH, then cast suppress magic (MoI, Clr 2, Sor/Wiz 2, Hex 2, 1r/Lvl). Carry your non-magical bag of apples or whatever into the protected area, and let the suppression expire. If you need more time, extend it or whatever.

but wouldn't suppressing the magic make everything in there...you know pop right out?

[Chemus]

Nope; according to dispel magic, "...An interdimensional interface (such as a bag of holding) is temporarily closed." So it's just a 'masterwork bag' for the duration of the suppression. See if you can get a Magic Aura'd Item that suppresses continuously by being attached to the bag

[kitep]

The Hoard Gullet spell also works.

[nijineko]

Soulbow PrC gets rid of the hiding problem altogether.

Changeling could hide a short bow inside itself.
Changeling could hide a long bow the same way but might walk with a limp.

+1 for soulbow.

[Kethrian]

Scout the place out, find an employee who you could disguise yourself as, make sure to note any passcodes or the like they have to use, and follow them until you have an opportunity to take them out (lethally or non, depends on your alignment).  Then you steal their clothes and apply makeup and whatnot to look more like them.  Now you can get past security with a weapon without worry, and without magic (True Seeing does not bypass non-magical disguises).

[Vizzerdrix]

Shapesand will get you whatever size bow you need, and even do so reguardless of magical detection. Arrowheads can easily be worked into any jewlery, as can fletching. The shafts are the hardest part to hide, but a corset, or one of those big dresses that had the framing inside would do just fine.

Edit- or the shafts can be worked into a framed pack.