I think the older versions based on 1.6 worked on Eclair, not sure on 1.6 though sorry I forgot the X10 was still running on that
![Frown :( :(](/styles/default/xenforo/vbSmilies/Normal/frown.gif)
You'd still need root access anyway which might be a problem on an X10, root was only achieved last week.
You could try bPlayer but it's not free and I'm not sure if it has that option, most other people would probably recommend DoubleTwist but I'm pretty sure that doesn't have the option to keep the screen on, might be 2.1+ also too.
Edit: This version says it works on 1.6 devices with eclair bits (what ever that means!)
http://development.piratemedia.tv/2010-05-27-music-mod-v1-5-mdpi-and-hdpi/