How can you check if your built in hdmi port is working under ubuntu 10.4? and what software would be needed?

Question

i've installed ubuntu 10.4 on my acer aspire 5920G laptop with built in hdmi and firewire and would like to use it on my hdtv + i'm looking at buying an external hard drive that uses firewire. Is there a way to check these ports are working before i buy and if not what would i install to get them to work.