This thing kinda shocked me, since it's definitely a totally unpleasant surprise.
I barely started Windows, and in about 1 minute, my NOD32 pops in, saying it found a trojan:

Win32/TrojanDropper.Agent.NDN Trojan

5 files have been deleted by me. It says this occured while accessing: WINDOWS/Explorer.exe(1) and YahooMessenger.exe(4).

Now, the thing which shocked me, was when I found 5 minutes later that one of my friends got his mobo fried because of another trojan.

NDM.Trojanb

Now, what action should I take? How dangerous are these trojans?