P4S5A/DX+ booting problem

I have this mobo for about 8 months now and I never had any trouble
booting, but for about a week now, I had a lot of problem getting my
computer started. When i boot, it cheks the memory, auto-detect my IDE
devices, show info about the IDE devices and then the computer freezes
there. I tried several thing that I tought was the problem with no
sucess.

Here are this CPU specs
- ECS P4S5A/DX+
- Intel Celeron 1.7
- Asus 7100 GeForce 2 MX
- Maxtor 30GB
- 2 DIMMs of 128 MB
- 300w PSU

Here are the things I tried so far:
- Booting without any IDE HD or CDRom
- Installed another PSU
- Tried another Video card
- I check the each DIMM of SDRAM, and also tried a DIMM of DDR
- Reseated the video card, ram, CPU
- I also check CPU temperature and it is normal.
- Installed latest BIOS update

Sometime, doing something like reseating the video card or RAM works
but, the computer freezes at next reboot.

I'm out of ideas now and its getting harder and harder to get the
computer to boot every time.

Thank