Tried the search function in both Memory and Motherboard forum sections for my situation and didn't find what I was looking for. So here we go.
MS 6533 motherboard ( http://www.pcstats.com/articleview.cfm?articleid=1172&page=7
6.0 PG bios
P4 Intel 2.4 g processor
2 PC2700 512 DDR 166.7 hz speed ram modules
350w power supply
windows XP service pack 3
I purchased a pair of PC2700 1G DDR SDRAM 333hz 184 pin memory sticks for my computer as the MS 6533 motherboard specs showed that it would support both that memory type and up to 1 gig in each slot, for a total of 2 gigs of memory.
Turned the machine off, removed the old 512 sticks from the machine carefully, placed the two new PC2700 1G sticks in and powered up. As opposed to a normal start up where I have a single short beep from the motherboard followed by my MB system splash followed by the Win XP page... I got an extended, long pulse of the motherboard beep with nothing showing up on the monitor. The beep pulse would end after 4 seconds or so, pause for that much time, and pulse again.
Did some digging and set my Bios manually to CL 2.5 speed and 333 speed for the SDRAM settings, rather than Autodetect or Automatic, respectively. Placed only ONE stick in at a time and tested both, and the machine continued to freeze with the extended beep on startup.
I set the new memory sticks to the side and put my old sticks back in and everything works fine. I wrote the vendor of my memory with this info for a solution, but figured someone out here might have some ideas.