1. Socket A board recommendation and 2. RAM problems!

I have an A7V266-E which I believ is faulty now. I've had it a while, so
returning it is not an option. I need a replacement to cater for the
following spec:

Athlon XP 2400+
1 x 512MB PC2100 Cruical RAM
1 x 1024Mb PC2100 Ebuyer RAM
2 x 120GB Western Digital IDE Drives (UDMA133)
1 x CD ROM
1 x DVDRW
AGP 4x or 8x
Firewire
LAN
USB2.0

Above are the absolute must haves.

My next question is :

When I installed my new 1024Gb stick to my already installed 2 x 256MG
PC2100 sticks, the PC only recognised an extra 512Mb so total was 1024Gb ! I
then removed the 256 x 2 sticks and the 1024Gb was only registering as
512Mb. Is this a faulty stick or a faulty M/B ?

I run a 400W PSU. Others have suggested a new PSU. yes or no ?