Since the Star Trek Blu ray has extras the other DVDs don't have, I decided to pick up a Blu ray player. I got the Magnavox on from Walmart for $78.

A few questions.
I just have a normal TV. Will it still be viewable on it using the A/V jacks? I know it won't be HD.

Other Blu-ray players have Ethernet jacks & USB jacks on them that this one doens't have. What are these for? Internet content of disks?

Is the Magnavox a decent player? If it plays the disks & I can watch the movie & extras, that's all I'm looking for.

If you're just looking for a basic player, this one should be fine. I believe it's the same one they've been discounting for a couple years now.

You can still watch it in SD using the A/V jacks.

Ethernet jacks are for a couple things: Download firmware updates and access online content. Firmware updates are good as they can add new features to the player, fix problems and provide better compatibility (some players require new firmware updates to play new movies if they're authored differently). Online content are downloads (trailers, new bonus features), information (news, weather - some of which are incorporated into the movie menus) and other online content (I think on some titles you can chat with others while watching the movie). Most of it is useless, but being able to download firmware instantly is nice (other players, like the magnavox, may require you to go online and download it from a PC and then burn it to a disc to put in the player).

The magnavox appears to be a Profile 1.1 player, which means it has "bonusview" (picture in picture). These are only missing the online content, but should otherwise be fine. I havent tried this player out, but for $78, you probably won't find anything else! When you do get an HDTV, you'll really appreciate it (and it can upscale DVDs)

Yes, every Blu-ray player has composite video and RCA audio outs (the yellow, red, and white AV cables).

Note that it'll probably output the video letterboxed, since HD video is always 16:9. With the Star Trek TV series, they pillarbox the original 4:3 video within the 16:9 HD frame. So on your TV, this BD may display windowboxed (black bars on all sides).

There may be a way for you to zoom in on the picture during playback, but I'm not real familiar with the SD display options for Blu-ray.

Yes, it's for the BD-Live features, which are downloaded from the internet and stored on a USB flash device. Most of these have so far been underwhelming.

It probably doesn't output the best picture, but since you're watching it on an SD TV, you probably wouldn't notice a difference.

Can you play files off a USB drive if I had USB ports? Specifically If I download an AVI file, can I play it on the blu ray to watch on TV?

It depends on the player. Playing AVI's off a USB drive is not part of the Blu-ray spec, so it's up to the manufacturer if they want to provide that feature, just like with DVD players.