copying files from subfolders into parent + renaming them

[tob10]

hi,

i have about 1200 folders each with jpg files named from 1.jpg to 15.jpg. The folders themself are named from 1 to 1200 as well. I have to move all the jpg files into one single directory. As they have all the same filenames, i'd need to rename them like <foldername>_<pic_name>.jpg .
They also could be just named from 1 to 500000 or whatever, i just need to keep them in order.

can you think of any solutions ?
thx for your help !

PS: No, theyre NOT porn pics !!!

PS2: I could use a Linux system to accomplish this as well.