Tsam, are you perhaps referring to VideoPad or one of the other NCH Software programs? Neither of those features (backup project files nor split track) appears to be present in Express Animate.
bty, I don't think you can directly choose a portion in Express Animate - you would have to either edit your project output afterwards in a video editor (which I think Tsam is talking about) or make a copy of your project, delete any earlier or later keyframes than the portion you want, change the duration of your project and, if necessary, move your keyframes into position to suit the new reduced duration.
If you only want the first part, you might be able to simply change the project duration.
Another option would be to render to an image sequence, delete those images you don't want, then convert those frame images into a movie (possibly re-adding any sound) in a video editor.
If your project makes use of separate compositions (like scenes) for each portion (with or without including compositions into one main composition), you can select and render only the appropriate composition.
Until NCH adds a feature to reset directories, if you keep a similar directory structure on the two computers, you should be OK - e.g. keep your project and items in C:\myprojects\thisproject or in C:\Users\USERNAME\Documents\Express Animate Projects\thisproject (where the USERNAME is the same on both computers).