Right. So take us through it doing the following steps:
1 Switch everything off (including monitor)
2 Switch monitor on
3 Switch PC on noting the flashes on the keyboard lights & what is displayed on the screen
4 At first BIOS beep, hit F8 a few times
5 Safe Mode should be offered
If Safe Mode isn't offered, then your keyboard isn't working (but then you'd have a few beeps telling you this or a displayed message on the screen).
So please, step by step report. As much info as possible.
It won't hurt to try the card again. If the symptom reappears, you can assume the card or the port is bad.
Turning off the machine is one of those controversial topics that comes up often.
You can save some power that way, and some wear, but turning off and on also introduces some wear.
Check your Power options in Control Panel, and look at things like turning off the HDs and the monitor, but overall a decent computer just doesn't care that much.
About the graphics card, do try,to uninstall the hardware first so that XP does a full hardware detect and install.
As to switching off, I'm quite certain where I stand. It's at night that the power companies do all sort of maintenance and spikes can occur. I've been switching PCs on and off for 20 years now without wear and tear being a factor - and I've never had any cold start problems.
Anyway, since the problem wasn't allied to that but seems to be a degraded graphics card, you could argue that keeping the card powered and no doubt hot is a true cause of wear and tear!