With modern HiSpeed drives and media that is designed to work at higher speeds, this:
i heard my friend say writing at lower speed is much much better..
is merely a legend these days.
You should be fine with good quality media at speeds around 12x.
Also make sure, that you have the latest firmware for your drive applied.
i got another question to ask..
u see, i purchased this samsung sata sh-s223f..
but when i check on my device manager it does not have 'sh-s223f'
here's the full name in device manager
-SATA TSSTcorpCDDVDW S SCSI CdRom
Well, that's the way, Windows handles drives that are connected to controllers which are not plain IDE controllers.
Screenshot below shows, what W2k device manager shows for a SH-S203B which is connected to a Silicon Image 3512 SataLink PCI controller card.
Depending on controller hardware, configuration and drivers, there might be some issues. Some of these are described in the FAQ article I mention in my signature.