For PC playback, you always want Progressive (no fields), as interlaced video never works well for PC or web videos. I would recommend using H.264 and then there are many presets available. Look for a "480p" option and try a sample - some say Android, some say iPad, etc. but they will all play on a PC since it is just an .mp4 file. By choosing a preset with Progressive output, that will deinterlace the video.
Note that if the original video is widescreen, then you'll need to make sure that the export frame dimensions are 854x480 with square pixels (1.0 PAR) since anamorphic video usually doesn't display correctly.
The MPEG-2 previously mentioned may also be just fine, but H.264 is the newer and more efficient codec.
Thanks
Jeff Pulera
Safe Harbor Computers