er, I could also do it too but out of spare chips ATM.
it is not so easy if you don't have:
-UV lamp for erasing
-EPROM programmer
in that case, here is what you do, cheapest way:
-download a *.bin image of version 7.0 (I'll send it) and save it onto removable media
-pull out two old v6.6 EPROM chips
-take *.bin and old chips to a friend or electronics store who has the lamp and programmer (it really shouldn't be hard finding someone). IIRC, they don't need to do anything fancy like swap bytes, just take care which chip goes where.
if for some reason you want to keep the old chips intact, you need to buy new EPROMs, they cost about 3eur here. you can find them on flea market, some old boards.