You need to install Fraps to watch them, they need the Fraps codec.
priater, you should recompress them with the XviD codec:
http://www.koepi.org/xvid.shtml
You also need VirtualDub (
http://virtualdub.sourceforge.net) or a similar program to actually recompress them. After you´ve installed XviD and VirtualDub start VD, open the avi, go to Video/Compress, select Xvid (there should be two entries, select the one that says "FourCC code: xvid" at the right side of the window), click Configure.
In the configuration window change the following:
Profile @ Level: Advanced Simple @ L5
Encoding type: Single Pass
Target quantizer: 3
Click Other Options, set "FourCC used" to DivX.
After you´ve made all changes close the window by clicking OK. Select File/Save as AVI, enter a filename, click Save and wait until it´s finished.
If you only wanna post screenshots use the Screenshot feature of Fraps and not the Movie feature.