Geforce 6100 vs. Nforce 4

There is no significant difference in speed between the 6100 and nF4 chipsets. The 6100 and 6150 boards are all microATX. Use 1GB of value-ram (2x512). Consider these choices:

EpoX EP-9NPA7I 939 nF4 ATX $65+7 6/06
http://www.newegg.com/Product/Product.asp?Item=N82E16813123264

Asus A8N-VM 939 microATX nF6100/410 $67+7 6/06
http://www.newegg.com/Product/Product.asp?Item=N82E16813131571

Foxconn 6100K8MA-RS 939 microATX nF6100/410 $59+7 6/06
http://www.newegg.com/Product/Product.asp?Item=N82E16813186085

The Asus is a known, stable mobo that's widely used in SOHO systems.
Foxconn is a lesser known brand that supplies many OEMs.
The EpoX in nF4Ultra form is widely used reliably by budget overclockers.

I believe that all 3 of these are good candidates. Google for reviews any that interest you, but info may be hard to get. Most people who use these boards don't know they have them.

The most likely culprits for instability in the boxes you build will be the quality of the power-supplies used and the cooling effectiveness.
I highly recommend adding a cheap intake fan in front of the HDD on the cases you use, and consider the following high-value PSUs:

FSP AX400-PN 400watt 12v:18+16a PSU 20+4pin $42+9 6/06
http://www.newegg.com/Product/Product.asp?Item=N82E16817104953

Get the cheaper of the two.

i personally Own a Biostar 6100 M7 - socket 754

dont mean to correct you over a small thing Newf - but the socket 754 can take up to 2gig of memory in it's 2 banks

the Socket 939 has 4 memory slots - im not sure but i think the max is also 2gig @ PC3200

i must say im totally happy with the motherboard performance wise

no stability issues and runs Debian 3.1 testing, just ducky i also have installed XP and W2k for the fun of it, though both dont currently reside on my system

hope this helps in some small way
got my Biostar 6100 at newegg for $60