No Onboard Video -> Screen BlankFollow

With a 440, I'm guessing that it doesn't have additional power ports on the video card that need power pliugged into, but you may want to check. Some of them did have 4 pin MOLEX power sockets, and if it has one, it will need to be powered to operate.

Your bigger problem is the Pavilion 7955 has an AGP 4x slot, if that really is an AGP8x MX440, which there were a few of them, then it isn't going to work with that computer.

To be honest, that computer setup is obsolete. You should be able to find a substantial and significant used upgrade computer for around $100 somewhere that at least has a PCI express slot for a video card and will be at least 3 years newer. For example I happen to know for a fact you can purchase a pentium D gateway E6500D with a geforce 6600GT PCI express video card in it from certain Washington State Government Surplus Online Auctions for between $50 and $100. If nothing else, if you haven't replaced the hard drive in that computer it will be failing sooner rather than later simply due to bearing age.

Some cards are, others aren't. It really depends on whether the card manufacturer included the capability in that version of the card. Others will just outright fail if they don't get the expected 8X signal.