I have two 2620 routers and one 2651, i have trouble getting the latest ios versions for this series. Can anyone help?

I was given a cisco 2620 router, once I power it on, it stops at snmp agent on host 2600 is undergoing a cold start. Then after a couple of minutes it says failed. But I'm unable to type any commands, it just sits there. Any ideas what the issue may ...

Do cisco 3750's support multicast? 2950's