Hi friends
I am using old p3 processor(933 mhz) with 512+256 ram and 40 gb harddisk.
I want to extend my harddisk capacity. Is it possible to update in to 500 gb
hard disk for p3 processor. Will it accept?

Yes it'll run but check first for HDD port. Most P3 supported motherboard use IDE instead of SATA so you have to make sure your motherboard has SATA port or the HDD can't be used on your computer.

Mother board name is VIA. It dont have the option to use SATA. Atpresent i am using IDE only. Is there any convertor which contains SATA type in one end and IDE type in another end ?

There's suppose to be one. A IDE/SATA converter in a form of card which you have to place it on IDE port and it'll convert to SATA which you can use SATA HDD for it...

So far I think this converter in unreliable because it doesn't work on my end and I've tested on several computers with same result but you can test it if you want. You can get it from your computer local store. They should have one for about 20$ for it.

don't forget the power supply has to have a sata plug or adapter as well,and you can still but large ide drives .just google it