@ OP - as you have not posted some more necessary infos ( cq50 has different models ) it's best for you to opt for a 1GB DDR2 667 Mhz laptop ram module :
Buy Transcend 1GB DDR2 Laptop 667MHZ RAM - Computers and Accessories - Infibeam.com
do note that this is only a indicative suggestion .. use cpu-z and make sure the timings/latency of both ram modules are matching with each other.