asus k8 dx se mb dying avenues to improve replace

My system currently is as follows asus k8 dx se mb-Athlon64 3000+ - 2 sticks kingston ddr 400-Nvidia 6100 128 with hdtv dongle-fusion 5 gold hdtv receiver card-creative sound blaster 2 zs-wd sata 2 500 g hd-eide wd jb 200 gig -4 external hds used for backup-new nec 16x all format dvd burner

Problems

mb is dying will no longer see dvd and frequently comes up with no os found and when it does boot takes about 3 minutes for grub to invoke so I can boot to xp or ubuntu
Seems to have at minimum bad controller.

Transcoding hdtv (1080i) takes an enormous amount of time for example 45 minutes (6 gig) takes 30 hours to transform to 4 gigs of xvid for dvd storage

I am broke and can not afford a total upgrade.

Tentative solution use inexpensive transition motherboards which will allow me to keep everything except cpu

an example would be the ASRock 775Dual-ViSTA Socket T (LGA 775) VIA PT880 PRO ATX Intel Motherboard .newegg.com/Product/ProductList.asp?DEPA=0&type=&Description=ASRock&Submit=ENE&N=0&Ntk=all
I could then upgrade to ddr2 and pciexpress then a new mb as I got the $$

My main concern is improving video transcoding speed. The MB is $57. A p4 3.2 is about $105 or I could get a dual core conroe 6600 for $312.

Please note the most rigorous game I play is solitaire.

My athlon was fine for everything I do except transcoding. Now I need to see how much difference in speed the 2 options offer. Is it best to go with the $162 or $369? If I go cheap now will I be better off with what I can buy in 18 months?

Any suggestions?