need to strengthen wifi signal?

[shay]

i need something to boost the signal to some rooms on the opposite side of the house, but iam not sure what to get. i was thinking a booster, but i heard repeaters are better.

any recommended ones or tips on what to get? please no downloadable "wifi boosters". id rather have a actual box, something small, and easy to set up.
my wifi box is a Cisco-Linksys E4200 Dual-Band Wireless-N Router and my computer runs on win 8. in case those matter on which booster/ repeater to use.
@falsi fiable

it is, but the signal is cut off right at the rooms. its very odd. its super strong but as soon as you go threw the doorway into one of the rooms the 5 bar signal drops to 1-2 bars.

we even joke that its because of "lead paint".