GeForce 4 Ti4200?

I have a PNY Verto GeForce 4 Ti 4200 with 64 MB. I was doing some overclocking with the card yesterday. I changed the stock speed of 250/514 to 275/570. Everything was running fine. Now today I turned the computer on and I heard a low humming sound coming from the case. So I turned off the comp immediately and opened it up. I took out the video card and reseated it in the AGP slot. I then started it up again and it gave me the same sound. I let the computer sit for 1 hour and then turned it on. Now everything is fine, and there is no humming sound. All the speeds on the FSB and the card are back to stock. I only overclock when I am benchmarking. Is it possible that I did damage to the card? The screen looks fine, and there is NO flickering on the screen. Is the card OK?

I know the sound was coming from the video card because I had a similar sound in my old computer and it was the video card. My old computer had a GeForce 2 Ti and it gave me the same kind of sound, so I replaced it with a Radeon 7000 and that computer is running fine. So when I heard this sound in my computer today, I immediately knew it was the video card. I opened up the case and turned it on without the side panel. I put my ear down near the video card, and that was where the sound was coming from. By the way, the fan on the video card is working properly.