the purpose of a fan is to either remove hear or bring in cooler air ,not increase temp! your friends are wacky .you should have a fan bringing cool air into the lower front of the case and a fan taking warmed air out upper the back ,

ok my cabiet dont have a fan to take air in all the fans take air out ,I fear this would create low pressure region inside the cabinet and reduce natural convection process . and more fans need more power ,does that increase the temperature ?

good ? ,but they don't use that much power ,and the power supply has a fan of its own to cool it

you can take some of the fans off and flip them 180 degs so that some are blowing air in. try to make sure the ones near the bottom are blowing air in, you just need a screw driver. (if they are already installed)

you need to circulate the air inside and as caperjack said cold air should be blown in at the bottom of the case, (just add some fans to the side panel its very easy), and make sure the fans near the top/back of the case are blowing air out.

if you need further help let me know and i'll send you some diagrams on some of the simplist layouts for fans. also if you can let me know what case you have or send a pic

regards

More fans blowing would equal more power, but only a small drain on your PSU. More fans is usually better, because it cools your system down better and quicker. If the fans are blowing in the wrong direction, just switch round the wires that connect the fan to the mobo, and this will make the fan spin in the opposite direction.

Honestly... unless you have some pretty wickedly hot equipment in there you really only need 3 fans. one at the bottom front blowing in, one at the top back sucking out and one on the top of the case sucking out. This should apply to any average gaming computer.

When you start adding more fans all you are really doing is interrupting the flow of air and instead of a large amount of air flowing over the hottest parts of the board you have a little amount of air dispersed throughout the whole case.

If you are really that concerned about heat. look into a BTX board. it's a new style of board that is built for cooling purposes. some day it will probably replace the standard ATX