I need to take the back cover off the dell d630 ---I've removed all the screws, but it seems that the front will not lift off like there is another hidden screw?

I don't know about the d630 specifically, but most laptops come apart from the top side and often require substantial disassembly to access the motherboard or other non-user replaceable components such as a hard drive or memory. The screws in the back hold components in place. See Latitude D630 Service Manual (http://support.dell.com/support/edocs/systems/latd630/en/SM_EN/index.htm) or XFR D630 Service Manual (http://support.dell.com/support/edocs/systems/latd630x/en/SM/XFR_D630_Service_Manual.pdf). If neither of those are your product, enter your service tag number in the support section of Dell's website.