I just got an old hp vectra 5/100 from someone so I can play dos games. Problem is I can't see how to get it open. It's unlocked, but it has no screws and doesn't seem to just lift off like other old computers. Any help? Thanks

Go to HP's website. Select "Support and Drivers", then "See support and troubleshooting information", and enter your exact model number or search on "Vectra" and select the correct series. Then look for a service reference or handbook under "Manuals (guides, supplements, addendums, etc)" which should indicate how the chassis comes apart.

Generally, for most older desktops, once the rear perimeter screws are removed, the top portion of the chassis slides forward several inches and then lifts off. However, getting them to initially slide can be a challenge often requiring prying with a screwdriver or other tool at a strategic location.