You'll get 480p output I'm pretty sure, nothing more, nothing less, unless your computer has a weak graphics card.
To view it, it'll probably be on video mode on your TV, some TV's have 1-3+ video modes, so flip around to see which it is.
The resolution if your TV may not be right for your computer, so it may looks all fuzzy and text may be unreadable.
It's best to connect a PC to a TV when you have a LCD TV, they will usually have dvi/vga input which will allow HD image and resolutions your PC are compatible with.