Warranty on emachine is usually very short and if you open the case, negates the warranty altogether.
let it run for several hours. (should have 0 errors)
Also try taking off the cover and place a fan blowing inside to see if it is a system heat problem.
Look at the HSF make sure the heat sink is clean.
Also, they usually put very samll PSU units inside, find the highest wattage PSU that will fit in the case, and replace it.
IMHO never buy emachine. I have seen nothing but problems with them. I know some survive but they are cheap for a reason.
My niece lives 100 miles away and has a system that freezes on her. She sent it to me where I added a HDD cooler and ran it for 48 hours. It ran perfectly so I sent it back.
It failed for her and wants to know what to do next. It is an eMachine she bought in January 2004 runing XP w/Service Pack 1; CPU=Cel2.6; HSM=256DDR; HDD=40GB.