Hey, i bulldoze my garden, just to drive the wife nuts
. Anyway, my only other point is, unless money is very tight, you really can never have to much space, and a 40 gig drive cost only a few dollars more than a 10. Then you also get into, what does the mobo support, can it be flashed, etc. etc., as you stated. I haven't seen a "new" 10 gig drive for sale for awhile, and the 20's are like 5 dollars less than the 40's. (Haven't really looked much, to be honest, but anyway). So i say save the money now, and get a complete upgrade soon.
Also running a DVD writer on those specs has to be very slow and a little iffy, anyway. I think the minimum specs for a pioneer 105 are like 700 mhz and 256 RAM, something like that, anyway. (mostly for the software)
My 2 cents only, yes it can be done, but is it worth it in the long run? Your PC, your choice.