Can changing your MAC address damage your network card?

My networck provider registered my mac adress to my ip ut i have two computers and i pass the newtworck cable from one to another. So one of them has a virtual adress and the other one hasn't.. the one that hast a virtual adress keeps restarting from time to time and does some strange noises when I download.. I am just curious if this can be the reason... I will take it to service one of these days obviously but I just want to know before that..

No. Changing the MAC address will not physically damage the NIC. You can change the MAC address on your PC without too much trouble. Check the reference links below.

That said, you should really consider buying a Linksys router for example, you can override the WAN side MAC address on the router to be the same as your PC (which you said is registered with your provider) and then plug in any number of machines on your LAN side. This way you will also have a hardware firewall and won't have your PCs directly connected to the Internet with a globally routable IP address.

99% of the time, you cannot change your MAC address on your computer. If you have 2 computers and you're transferring the network cable between the two, either it will work or it won't, no damage done. If you have 2 network cards in the first computer, and you're using Internet Connection sharing, no harm done.

If you're planning on getting more computers to add to your network, you might want to look into getting a router.