I found the support page for the EMACHINE T3042 MOTHERBOARD, there are some links to their tech support at the bottom of the page. The manual didn't have any usable illustrations, you might want to see if there tech support can chat you through it or send you a picture of the board.
Actually that link is for the T6524 but that is easily fixed just by changing the model number in the link.
As for the documentation, eMachines are owned by Acer and as such, they don't release service information related to the motherboard.
I Searched through the entire service manual and there was nothing in it pertaining to Jumpers, pin outs or anything else to do with the motherboard.
About the only information they really give is generic stuff such as how to upgrade the memory, connect the media panel and some other minor stuff.
Acer has taken support to a new low where you're lucky if even the techs have access to the information you might want. Acer has done this to Gateway and to Packard Bell as well.
Good Luck getting the Jumper information.
Your best bet is getting the default settings from someone else who has the same system unless you can find an image of the motherboard on Google image showing the jumpers.