how experienced off road are you? how tall?
there are shorter bikes like the serow, and Gas Gas Pampera, and there are full on Enduro bikes.

what kind of budget, and how serious do you want to be.??.....
fun can be had on a budget, i once did a whole winter on a DT125lc, that cost me £80 (altho i did a fair bit of work on it), but now run a WRF250...

one last hint, dont buy a 4 stroke that smokes, and dont buy a 2 stroke if it doesnt!!! :-)

if i had to pick a cheapish bike for a newbie, id recommend a KMX125, the DT has better suspension but a PANTS engine, and wont be as cheap as a KMX year for year.......remove the washer from an inch inside the front pipe on the KMX and youll have a good little lightweight winter green laner.

shame im "Physically unable to ride offroad" at the mo, as i could have shown you salisbury plain! if youve got a bike in about three months from now, give me a shout......

cheers.