1 or 2 memory modules?

[jimmysize]

i have a compaq presario sr2009. i found out the motherboard specs
here and it says:

Single-channel memory architecture
2 x 240-pin DIMM sockets support unbuffered non-ECC 400/533 MHZ DDR2 memory modules
Maximum HP/Compaq approved memory is 2 GB

there are bits of this i understand but i'm not sure if i can use Corsair TwinX XMS2 (2x512Mb) i know they are ddr2 which is fine, but they are pc5400 (667). Does anyone know if they will be ok on my PC? i currently have one 512Mb module. would it be worth getting these 2 modules over getting just another 512Mb module of similar spec to the one i already have? i don't use the Pc for games but i do end up with a lot of windows open for work and this slows everything down quite painfully hence the need for more ram (i had the same problem with a laptop and a memory upgrade sorted this nicely). basically i'm asking:

is it worth getting an extra module or 2 new matching modules to make up 1Gb?

thanks in advance

Jim

[honvetops]

Welcome to computerhope.com  !!!!

Intel® Pentium® 4 Processor 524 supporting Hyper-Threading Technology
• 3.06 GHz, Level 2 cache 1 MB, [highlight]533 MHz[/highlight]
Operating system installed
Genuine Windows XP Home Edition
Upgradability
Windows Vista Capable PC
Chipset
ATI RADEON® XPRESS 200 Chipset
Memory slots
2 DIMM sockets
Standard memory
512 MB
Memory type
DDR2-SDRAM

*I*  would just get another stick of the 512  you already have*
You will have a nice performance boost.  The key on the memory is , don't buy any ram on your board over  533 Mhz..  <
It's not supported by your motherboard.

I am told using 2 sticks of the same are better than 1.

[jimmysize]

thanks a lot for your help. i couldn't find another module the same as what's in there already (made by hyundai and not that great). so i went for a matching pair of samsung modules for not that much. thanks again, i scoured internet guides but cant make much sense of compatibility issues.