Q:

Where should I post about computers / gears obsolescence and renewal in a company? 

I'd to ask a question about how a company should manage efficiently to renew its stock of computers.  It will be about policy but also the technical and human criteria they should consider for their final choice. 
This sounds like this would fit the "workplace" site, but this also quite technical since I think you need some computer skills to answer it. 
Do you have any idea where this should go? 

A:

Server Fault, maybe. 

Server Fault is a question and answer site for managing information technology systems in a business environment.  It's built and run by you as part of the Stack Exchange network of Q&A sites.  With your help, we're working together to build a library of detailed answers to every question about server, networking, or related infrastructure administration. 

Which seems to cover your need. 
Log into any active/applicable chatroom there and pitch the basics of your question there - they'll soon tell you whether it's a fit or not and help you get things into shape, if needed.