When I was a Windows user, I wrote this utility to convert a series of frames (in Targa format) into an AVI.

Download:

Example usage:

tga2avi out.avi 25 abcd%%04d.tga 1 100 1
(will convert abcd0001.tga through abcd0100.tga into out.avi)

tga2avi out.avi 25 img.%%d.tga 2 12 2
(will convert img.2.tga through img.12.tga (only evens) into out.avi)

It'll only compile under Win32 because it uses Video for Windows calls to write an AVI.