OK, let me try to help you out in whatever way I can...
Incase you already haven't done so ...get yourself an Import export code. Computer parts are freely importable, so you don't need any special licence for that. The IEC code above should be good enough. There are agents who can do it for you, but its just an easy form and you can do it yourself too. Just costs some 1000bux. Here is the link
http://www.ap.nic.in/jdgft/iec.htm
This is how the duty structure works...
First calculate the CIF valve (this is cost + insurance + freight). All duties are on CIF value and not on the cost you purchased the item for. This is also reffered to as the "landing" cost.
First off you need to classify your commodity you are importing into a commodity classification code based on the Harmonised System of nomenclature (HSN). Your agents will be able to tell you the exact code. Basically all computer parts come under 2 classification codes. Just be careful before importing anything with a motor or pump, cuz these things even though they are computer parts sometimes the customs will put them under a different classification code and hence a different duty structure will apply.
For computer parts the basic duty is free for most of the parts. But then there are other subheadings like Additional Duty (16.48%), Addl. duty of customs (4%), education cess (3%). Totals to almost 21,653%. If you are importing into Mumbai then there is also Octroi (5.5%).
Thats pretty much it as long as importing into india goes. There are export laws governing the contry you plan to purchase from. If your supplier is handling the export part of it then you are fine, but if you plan to purchase from the supplier first and then export yourself in that country then you need to study the export regulations of that country too.
PM me if you need any additional help!