sometimes when using my Fuji S100fs in video mode I forget that I should be filming in landscape format and flip to portrait

the resulting video is on its side...is there a way to correct them easily? ....

http://www.virtualdub.org/index

Virtual dub will do it.

Not sure which filters are inbuilt but there are at least two filters to rotate, one free rotate one in 90 degree steps.

Bit of a difficult program to find your way around. You load the video file, select video, filters and add the filter you want. Then save the output.

Thanks for your help.