How to build server with leftover pc hardware

I can't just buy the best of everything. So what do I need to concentrate on to get an economic build.

What pc parts can I save money on which should I invest.

I'm planning a low budget server from 2 to 3 generations old hardware which is lying around. I will buy some parts if necessary. It should stay a quiet system.

It should be powerful enough for a "windows 2012 server" that runs a website with asp.net and MS SQL and some experimenting that doesn't make me grow a beard for every action.

I'm also open to some creative answers like, just using an old notebook which would be kind of handy, if some explanation to the pros and cons is involved in the post.

Thank you for you ideas!

it will be cheaper to buy low end 1155 stuff than to buy older higher end stuff, the lower end new stuff will perform as well as the high end old stuff

if you could tell us all of the specific parts you already have that will help us

using a notebook with a Ivy bridge i3 should be good enough for what you are doing and it will use almost no electricity, while just being used to host a web server you can set it to where it just turns off the screen when you shut the screen and turn the note book upside down for better cooling

could you briefly explain just what the website, asp.net and MS SQL intail, I don't really know what those are but I can't imagine they'd need more than this unless you're a huge website

CPU

Mobo

Case/RAM

PSU/HDD

I imagine that even that is overkill for it anyone else have a opinion

what old tech stuff do you have right now 

I know old stuff is not as exciting as new, but sadly I'm talking about dusty thing like: 1.3 GHZ Athlon, SD-RAM, ATA-133 HDD conectors.

What do you think the bottleneck for the server would be ?

Should be good enough for 6 month or so until I move everything to an actual hoster with virtual machines instead, but I need to do some experimenting on this machine first.

the ram and the CPU, HDD is fine, do you have a old case and PSU to use?

if so this is like 95 and will perform waaaaaaaaay better

CPU

MOBO

RAM

if you have a case, PSU, and Ide HDD alread then that is the cheapest build you can make

 

or you can buy a 775 CPU like THIS for dirt cheap on ebay and then get

MOBO

RAM

this is likey a cheaper method

yeah thanks i think we are getting there!

And Yes PSU and Case are available. HDD is questionable.