Why do I have to reseat my video card in order for my computer to work?

maybe your chord is not fitly snugged in there buddy? maybe its a dying gpu

who said you need to "reseat" it?

do you have drivers installed?

do you have multiple displays connected to it?

Turn off the computer and pull out the video card. Get a clean pencil eraser, preferably new, unused. Use that to wipe the gold contact points on the foot of the card to make them shinier. Be careful not to touch any other electronic parts (rubbing too hard might push them off). Don't touch the contact points with your bare hands. The natural oils of your skin can block electrical contact. Make sure the contact points are free from debris before returning the card into the slot. BTW, use a blower on the slot (and all over the inside of the CPU) to make sure nothing is blocking contact there.

If you can blame an alignment problem, bending the mounting tab or tweaking how the motherboard sits to make them fit better might help.

my offhand guess would be that your power supply isn't providing enough juice to start up the gpu and the cpy at same time.  it's worth checking out ... find a PSU sizer app on the web and plug your parts into it ... see what it says for the minimum power supply size.  [I use the one on the power supplies page at newegg.com]