I did my purchase, not as I originally intended but almost as good. I decide against going to the ComMart expo since I figured that any shops that went there would not bring large harddisk, as it is not really mainstream despite the going price. And I think I made the right choice since when I visit one of the shop I knew in Pantip (this shop is probably one of the oldest shop there, it's been there started by selling pirated softwares and games in diskette) The owner remembers me and we chat a bit. She told me that this times the expo is concentrated on notebooks, so most of what shows there will be notebooks and little else.
After walking around Pantip for a while looking at all the price, I decided to follow one of my friend's advice to get Maxtor brand. There seems to be only a few shop that carried Maxtor harddisk for some reason... Perhaps it's because Seagate had up the stake by increase the usual gauranteed time to 5 years. Still... I decided that a longer working harddisk with shorter guranteed is better than the vise versa scenario.
I went back to the shop that I had my latest upgrade with them. After telling the salesperson what I want, he told me that 300 Gb harddisk would not be recognise by most mainboard yet. They can manage that but it will required for me to take the machine to them and it would take all day. Since I did not carried my computer with me, nor I would wants to, now that I knew it just one harddisk that cause all the problems.
So after all said and done, I bought Maxtor 250Gb IDE for 3,500 baht. Which might be for the best since Maxtor IDE harddisk have 133 cache compared to the 150 of normal S-ATA. I had some experince with installing IDE and none of S-ATA.
After I got home I install the drive into my dusty computer case with the newly bought scrwedriver. I was a bit worried at first since the harddisk did not show up on the BIOS loading screen but after XP has loaded up, it recognise the new harddisk right away and after the startup has finish the harddisk is ready to be use (read filled up *wink* *wink*)