PC does not boot

I know you may have seen 10's of threads with this subject over the last few days. Why i post another is because, after reading through a lot of the similar threads, my problem still persists.
I have got a Dell Dimension 4100 PC and recently by mistake i took out the original memory and inserted a 256 mb PC 100 dimm the PC performed the POST and then displayed a message memory size decreased. I switched of the PC removed the Dimm put back the original DIMM and it does not do anything.
The fans switch on, the Key board LEDs light up then go dead, the CD Rom lights switch on and the HDD makes the normal whirring sound but there is no display.
The Floppy light does not come nor there are any beeps or POST.
I tried removing and putting back all the cards one by one but they all seem to be fine, but still problem persists.
I removed the Dimm and the Mobo gives 3 short beeps.

these are specs:
CARD (CIRCUIT), PLANAR (MOTHERBOARD), NO SOUND, DIMENSION, 4100, A
Intel PIII Processor, 80526, 1GHZ, 256, 133, FIBER CHANNEL
Dimm, sdram, 128 mb, 133M, 16X64, 4K, 168pin
CARD (CIRCUIT), GRAPHICS, VIDEO, 32M, MRMGA2, DIMENSION
HARD DRIVE, 40GB, I, 7.2K, 20/P, IBM-ERC

Guyz please help me out. I need to get my Project done.

(^~;?(That the no-memory like error beeps means that bios is active.)

Then most doubtful now is memory I suppose. Check memory first. But if you are unlucky, circuits around memory might have become ditchy.

hi,

Thanks for the advice i checked the DIMM on another PC it works. please help.

(^^;(Though there's no doing if the circuit is damaged, check condenser (capasitor now?) head whether they are swollen or not.)

Remove all peripherals unnecessary for boot, no hdd, no cdd, floppy only.

Next change Video Card.

Try CMOS clear by jumper and boot, several times.

Remove CMOS battery a while and attach again.

Change CMOS battery.

Thanks. i'll do that and hope it works.

How goes the progress, Vikas?

Hi Guyz,

I think my mobo has fried near the memory slots area. I checked for any leaking capacitors and could find none. so ithink i have to change my mobo. anyways, guyz thanks for all the suggestions and advices.
vikas