For you, the cheapest PC you will probably find is at a recycling center. Now if you want a brand new one I really recommend that you look for some merchant's web sites. This is not a merchant's web site.
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"Don't disturb my circles." translation of Archimedes last words
A second-hand one as all have said, is the best. But while you are not bothered with screen and ram, you want to use it for CAD. Which package ? Makes some difference. My experience is with SolidWorks 3D CAD. Minimum RAM for good working is 2GB. i have a Dell Inspiron 6000 of 2005 vintage, 15.4" screen with 1920x1200 resolution. Good performance even without a graphics card.
If i get a new long-term contract, i might upgrade to the latest Dell Precision laptop. In which case, i may be willing to sell this one. Not less than Rs 20k though.
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Nothing worthwhile can ever be taught, it can only be learnt.
Just open any news paper classified section . you will get plenty of options.
this is not the place for trade . Some serious technical discussions is always here.
Use this platform to upgrade Or share your technical knowledge. No trade or sily timepass questions.
I request ,moderator of this site, should carefully chose the questions. Because i found that discussions remains alive for max. one week. Because members get involved in other discussions everyday.
For your application it will be free. If you have friend who is taking computer to recycling take from him. This is low cost computer. I would have given free but I am in US and shipping cost will too much to send you
I think you need to be more specific about what kind of CAD you intend to run. Lots of CAD programs can be very demanding of hardware and screen resources.
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If you spend all your time looking for people and things to complain about: trust me, you will find plenty to complain about.