The 3 beeps are a clear indication of a memory issue and if you have loaded BIOS default values (nevermind trying to manually adjust ram characteristics within the BIOS - if all the modules have spd capabilities - which they should, this should all sort itself out automatically). If it doesn't, you have the wrong memory type.
If you want the authoritive word on what memory works with the DP45SG here's the relevant memory page. HTH
Here is your answer:
This board only accepts up to 8GB of DDR3 RAM, (yes we all know) however the density of that RAM is WHAT MATTERS!!!! I tryed 8, yes EIGHT different RAM brands and configurations till I got it right... You must use 2GB sticks to get 8GB, however most of the ne RAM (if not all) is SINGLE SIDED!!! When you look at the Intel memory specs it specifies 2GB sticks that are double sided, you might be buying PC10600 and 1333 mhz blah blah blah, but if it is not double sided as in 16 single chips on the stick it WILL NOT WORK!! Double sided is getting HARD to find. My local Frys only had one 4GB kit in stock, but Amazon does stock it though Newegg has discontinued it.Corsairs website claims some of their 1666mhz stuff will work on this board but I'm not spending the cash to find out after this dissaster!!
http://www.amazon.com/gp/product/B0014BOQ54/ref=ox_sc_act_title_1?ie=UTF8&m=ATVPDKIKX0DER Title is wrong as it states 10666 but the tech specs details it out at 10600 same as FRYS.
i got these problem
2x1gb ocz intel extreme edition ddr3 1333mhz pc3-10600 ( http://www.shopping.com/OCZ-OCZ-Intel-Extreme-Edition-Dual-Channel-2048MB-PC10600-DDR3-1333MHz-Memory-2-x-1024MB/info) these are working on my sistem with no problem
and i want to ad these:
2x2gb Corsair TW3X4G1333C9A XMS3 4 GB Memory Kit fro PC3-10666 1333mhz 240-pin Dual Channel DDR3 ( http://www.amazon.com/gp/product/B002D11C6U/ref=oh_details_o02_s00_i02 )
i cant them to work, i have updated my bios to 125, tried to raise the latency to 9 9 9 24 1.5 v as the corsair said it should work and nothing.
i think the corsair modules are double sided as you mention, even look at the corsarir tech support page and they say that it is full compatible with the motherboard, what do you think is the problem?