Hey i have a emachines

Question

Hey i have a emachines E4028 pc its a UK addition so you wont find it on emachines.com anyway my problem is i tried to replace a ram stick the other day but then i found out it wernt a pci stick sso i then put back the old on in wen it was i turned on the pc and it wont boot up the fan stays on the screen is black?? can some1 help?? ty