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The liquid metal sounds expensive.Probably not afordable for a home PC.I think a refrigerated window type air conditioner could be modified to run some cold air into the PC case.The only problem I see with this is moisture condensation.Maybe a dehumidifier  for the PC room so the  air circulating  to the AC would have less moisture.
One other idea how about a PC inside of its own freezer(home type freezer self defrosting type) Unless you like cold then a walkin freezer for your PC room.

I don't like the water cooling idea much.I web surfed & found an interesting unit.It didn't have the price though .One of those contact for price.Nothing much covered the condensation effects of cooling the air entering your PC.Thats not a problem with fans but water.refrigerant,or electric(like the ice chests that work off your car battery current & don't use refrigerant)If anyone doesn't think about the moisture in the air look at the puddle your car leaves when you park after running the air conditioner then imagine blowing that into your PC.This unit still looked interesting.
http://www.barrytechsales.com/downloads/ko_refrigerantchiller.pdf
K-O Concepts
HS- 4 / 115

Remember this cooling system? If they only could have made it smaller so you wouldn't have to give up two of your drive bays. It mounts into one bay (lets say at the top), but blocks the bay directly below it. If you mount it in the bottom bay, you block the floppy (which wouldn't be so bad), but I still use mine for certain drivers that come on floppy disks.

Overall, this unit will keep your system temp way down and, in turn, drop the temp on your processor. The idea is there...just needs to be more compact. 

PC AirCon PAC 400

Those are some great ideas cholla. If I were crafty enough, I would try to design a prototype of some sort for demonstration. Stopping condensation would be a big factor in the design. I definitely wouldn't want a big mess inside my case.  Just thinking about dealing with a hazzard like that pisses me off!  Go to plug in a new peripheral device and end up getting shocked to death.  Not good!

If you are a good designer, you should invent something. You have all the ideas in your head already. Sketch a few out and sell the design for millions! 

If you add a filter, the air inside will have less dust particles, but you're gonna need a better fan and time to replace/clean the filter. If you have a properly made case cleaning dust from the fans won't be so hard. For air cooling you'll want cool (as cool as possible) air entering the case, which can be a problem sometimes. My room for example gets really hot and that's why I can't OC at all, because everything getting 'cooled' by hot air. The solution would be an airco. Pricy thingy of course.

I know of self-made air ducts from and to the processor fan, to lower temperatures, but no commercial product just for that purpose. The NV Silencers for videocards do have an exhaust, so that idea is already patented I suppose.

I did some work on the vent system like I was thinking about.These are the link for the parts.
http://www.smarthome.com/3011.html 3016  This is the inline exhaust fan you would need to put a 115 volt power cord on it.Or if you put it through the ceiling into the attic probably wire it directly to the house wiring.This is a inside vent fan.(they do make some outside inline vent fans but the are 4 to 5 times more expensive.)
http://dwincorp.com/product_info.php?cPath=57&products_id=296&osCsid=d1d4a60d28cb52714f39104782bb8987  This is the link for the 4" insulated flex duct.
http://plumbing.gillroys.com/Heating/Dryer_vents_and_hose/Bathroom_Fan_Eave_Vent-s264954.html This is a vent I found that looks like the flat part facing the PC power supply could be screwed then sealed in front of the power supply fan & the flex duct clamped to the other side.
The reason for the fan being this far away is to take the noise & heat out of the PC room.If you use an outside fan you could go strait through the outside wall & the fan noise would be outside.
With the inside fan Cost would be under $100.00 with the outside fan about$225.00
I decided I would post the outside fan also.  http://www.fantech.net/fr.htm
below is a diagram & photos of the parts.

Cholla, It's nice to see some custom venting.....almost every case I have has been modified in some way or the other......Dremmels, drills and jigsaws and snips....good tools to have on hand when it comes to case mods.

Your system keeps the noise outside? correct? that a good thing, but in the summer are you ducting hot air in?  In the winter you could suck all of the cold air from outside and overclock the brains out of it!

Anyway nice idea, got that gray matter working!

Buzz ;)

OK if you have an air condition running inside you would certainly cool it off, or even if the temp is lower inside than out......the ducted fan noise is up in the attic right? Not in the same room as the computer??

Will there be any condensation issues to deal with??  really hot air in the case cooled down real fast??  probably not till you reach the outside vent part.....and it wouldn't matter outside......just don't want you to get a "Buzz" from electricity!!

Buzz