Dell says that the error code you are getting is
* Memory failure within the first 64 KB of memory *
http://support.dell.com/support/edocs/systems/dmum/codemess.htm#post_beep_codes
This is not the type of fault you would get from incorrect
memory, rather seems to be either bad memory or bad mobo.
Given the history of this machine it would be my guess that the
mobo is the problem.
Are you certain of that?
I mean, if the memory weren't working properly, wouldnt' the
first 64KB, be the first to fail when attempt was made to
load up the firmware (BIOS)?
Granted we don't know the history of the system, that it
wasn't whole is not a good sign, might suggest there was
already a problem but I would try to find an old DIMM to try
in it, even if it's something really old, a PC100 64MB
module or whatever... Even a module instable a the FSB
speed might work well enough to get a POST, or possibly
there is a jumper to lower the FSB speed to 100MHz... I
doubt it on a Dell but stranger things have happened.