It would help if you explained:
a) what settings you have used - compressor (codec), framesize, bitrate to name a few
b) how you intend to distrubute your film - over the web, via email, on DVD, on CD, just for your own use on your harddrive, to be played in a standalone. This has a HUGE bearing on the quality/file size trade off.
c) the specifications of your PC
Infact, this question can't be answered without at least the answers to those questions
