New PSU and MOBO which 4 pin should I use

For the 20+4, you use the 4 that clips onto the 20,
the other 4 pin is for the cpu, should be a plug nearer the cpu socket for that man  
Moto

thanks MOTOPSYCO. My motherboard combo only has one 4 pin, nothing near the CPU. The other 4 pin on the PSU wires was bundled up with the perifial connectors.
This board has a spot for future CPU, maybe it's for that. I don't know. this is my first build.

What MOBO do you have - most newer MOBOs will have a 24 pin MOBO connector and another 4 or 8 pin connector for the CPU - Old MOBOs used to have just 20 pins for the Mobo and either did not have or have a 4 pin for the CPU - so it all depends on the MOBO you have !

normally the 20+4 will be used for the MOBO (either using just the 20 pin and leaving the 4 pin loose or using all 24 pins - but it is almost always just a single plug not 2 seperate ones !!) then the other 4 pin connector from the PSU will be used for the CPU plug if it is there or is not used (only started being used as CPU starting requiring more than 75W for the CPU which was all the 20 pin MOBO connectors could provide)

I have a ASRock K8upgrade. The 4 pin that slides off the 24 pin connector fits in the 4 pin slot on the mobo but after i looked at it the shapes don't match up two are square and the other two are rounded but the rounded part is facing the wrong direction no matter how you turn it. The other 4 pin from the PSU fixs correctly. the one that fixs correctly has two black wires and two yellow. The 4 pin on the mobo says ATX 12V 1. This makes sense to me that if it only needs 12V both yellows would be 12V each and the black ones would be grounds Could i plug the PSU in and check it with my multimeter? The other 4 pin from the PSU has orange yellow red and black. Both the 20 pin and the 4 pin are close to the CPU sempron 3000. I know its cheap stuff but this is my first build and i don't want to lose to much if or when i screw up it's more for learning.

By the way the PSU is a 400 w Kpower By kentech. Here's the specs: 3 peripheral, 1 floppy,1SATA connector,1ATX 12V P4 (square 4 pin connector),1 x 20/24 mainboard connector( work on both 20 pin and 24 pin motherboards)

OK the K8Upgrade MOBO has a 20 pin Mobo connector so you will use the 20+4 pin with the 20 pins connected to it and the 4 pins just left unattached and then use the 4 pin that has the proper shapes for the CPU plug (they pretty much design them nowadays so it is pretty hard to mess up - so when you would try to use the +4 pin portion of the 20+4 it wouldn't fit !)

Thanks so much! One less thing I have to worry about when things don't go smoothly.

Sorry I couldnt get back sooner, nightshifts hehe
Glad you got sorted man, happy building and come back if you hit any more snags  
Moto

I'm sure I'll be back going to try to do this without formatting the hard drive because this OS is win 98 with XP upgrade but I don't have the upgrade disk.

MOBO worked. I got impatiant and just formated the hard drive. then reinstalled windows 98. had to know if everything worked. It did. Now maybe a new OS or something. Thanks for the help everyone.