Batch conversion of images?

My Satellite Setup
relook 400s with 1 meter wingard dish/invacom qph-031 lnb/sm3d12 motor(tuner1)
2 dish 500 with disecq for tuner 2

twinhan 1020a pci card in a 2600+ mobile athlon clocked to 3300 mghz.

dishnet 301 rec rom 10 to 103 conversion.
My Location
hi, ive been playing with slideshow in radio window, and have mplayer, a file to convert jpeg to mpeg, so the relook can use them, i have to resize my pics first, say i do 25 at a time, i resize all 25 to 720x880 then rename them all sequentially for easy c/p.

then i open a cmd window and goto mplayer directory and c/p this cmd line in:
mencoder.exe mf://relook1.jpg -o relook1.mpeg -ovc lavc -lavcopts vcodec=mpeg2video -of rawvideo

with relook1 being file name. so i just change name and c/p the line and bam, make the image. but doing this one at a time is slow.

is there a way to do say 20 or 50 at a time?

i tried this :
mencoder.exe mf://*.jpg -o *.mpeg -ovc lavc -lavcopts vcodec=mpeg2video -of rawvideo

using the * for filename, it almost seemed to have worked, it said in the dos window it rec 63 files for conversion, then never made it past the 1 one.failed to open file.

has anyone done this before and is it as easy as a cmd line? id like to make a couple 500 pictures for slideshow!

any help appreciated.!