All ,
I am planning to host website and planning to buy hardware for that

and am expecting 200 website to host on the server and going to have 30 mb of space for

and on average 100 people will be using different website .

Could any one guide me how much memory i have to look for and CPU speed
and bus speed

Thanks in Advance

You want a high-end server CPU like a xeon, and prererably more than one.
You should invest in an actual server pc, its better build quality and more reliable

Something like a HP/Compaq server

you are going to host 200 different websites? for that you'll need a dedicated server probably. actually 200 sites without too much computation on the serverside, like forums or simple portals and blogs, can be hosted on a pentium 3 pc with 512 memory. but if you want to be serious about it and go the extra mile, either buy a normal rack server, something like Dell PE1435SC should be anough, and Dell PE1950 should be really grand for this.
or just rent a server on a farm somewhere - you'll have it up and ready for you with all your needs inside already.

Yeah, you need 515 minium for any database.

Get a brand name server, a dell or hp/compaq - unless space is in short supply, get the tower model, not the rack one as its easier to replace/upgrade the components in them and they are cheaper

Xeon is the way to go, and you probably want 2 to 4GB. I wouldn't get a rack server unless I was planning on adding more.

yeah, dont use 3b though, as windows will waste it, either use 2gb, which i tcan handkle iout of the box, or 4gb, which it can handle either by using 64 bit, or the /3gb and /pae boot options