Making a mini PC from a Laptop motherboard

Hi all! I am thinking of taking a old laptop with a busted LCD and keyboard and make a PC that would have only the motheboard and the HDD from the laptop. Aslo I would make a case (small box) out od aluminimuim or/and plexiglass. 

I would like to see your opinions about this project before I start doing that because I need to invest some money in some other parts. The idea would be like the Macmini in the idea that people were saying that it is cheap ti give 700$ for a i7 CPU laptop (no one mentioned that it is the mobile version that runs on 2,4Ghz) and if you take a 700$ laptop you have an LCD and all the other stuff plus the hardware equivalent of the Macmini.

I would like to see some constructive suggestions because this is going to be a build just for the fun of it and maybe be used for a HomeTheater. 

I think it's stupid id I'm honst but if for some reason you are going to waste your money on making a bad pc it's not my choice.

if I'm Honest*

As I said, it's just for fun, I dont know if anyone did it before and knows something about it. I am mainly interested how to mount the board and HDD on top of each other (I want it as small as possible)

there will be no dedicated cpu, no point just do mini itx

I think you got the wrong idea about this. I have a gaming PC (i7 2600K etc) but I have this laptop with a AMD 5200 mobility graphics. The only cost would be the RAM and the case with I would make it myself, as a hobby or personal project for fun. Also, the main usage scenario for this to be able to carry it when I go somewhere to travel and being able to connect it to a TV or monitor fo movies and web. It should be very small since the motherboard is like half the area of a laptop (cca. 20-30x20-30cm).

i did this to my old hp laptop. the screen broke, so i opened it up and removed the hinges that kept the screen assembly attached. then closed it all back up. you get amazing batt. life, and if you keep the keyboard and mouse you can just plug it into a monitor and go. however... you said you want to make a custom enclosure. assuming you have a hand held router at the least, go with MDF. lexan / plexyglass / acrylic  are all expensive, and i can see electrical issues with aluminium.

 

also, if you do go with this idea, do NOT disconnect the wifi antenna wires, instead lift up the keyboard and zig zag them, and then adhear the aluminum end peices to the metal plate under the keyboard.