I was wondering if i can connect my imac to my sony 42" hdtv through the mini-dvi connection on my imac and use it as a second display? Also would the tv be able to support HD resolutions, since it's an hdtv?
It will work fine once you set the 2nd display to the correct resolution/refresh rate in system prefs. The iMac can handle external digital displays at up to 1920x1200 so you're covered for both 720p and 1080p HD.