All have a CMOS battery. Desktop and Notebook PC's.For laptops it is known generally as the RTC battery. Real Time Clock battery.
http://www.tim.id.au/blog/tims-laptop-service-manuals/#toc-gatewayThe above link is to a free Service Manual.Go to the heading Gateway 400. (400 in blue)Drop down to second line, scroll across and left-click on -NV59The service manual is in PDF file form.The computer you are using now has Adobe Reader on it, which uses PDF files.After you click on the file name (NV59) it may take up to 30 seconds, before the first page comes up.It is a black vacant page. Bring your mouse cursor towards the bottom/middle. In the navigation guide that comes up, go all the way to the right, and click on the red Adobe PDF icon.You are now looking at the older style, which has a navigation bar at the top, and Bookmarks menu, etc. to the left.Go to the left side, and click on the Bookmarks icon. Blue 'ribbon' with triangle cutout.(3rd icon down)Scroll the Side bar down, left-click right on -Replacing notebook components(I reduced the view size to 75 percent. But I am using a Philips EN-V 26 inch HDTV as a monitor. (And an HP 2009m. Running dual monitors)Zoom In icon at top is the + sign.Zoom Out icon is the - sign.Zoom Out to reduce the view size)Left-click on - Replacing the Modem BoardYou are on Page 83 for the PDF viewer. The actual page number for the Service Manual is 77.Go to Page 78.Now,....removing the RTC Battery, and leaving out for a short period, (OR Long period) of time, will NOT do the trick.There are capacitor/s which store a SMALL amount of power, and keep settings, such as a BIOS password.The procedure is to short the capacitor/s, and drain the power.This is usually done with a jumper wire across two small copper pads.Go to Page 46 (PDF file. It is Page 40 for the Service Manual)Regards,joecoolvette