Using VirtualDub

When i try to play one of my avi files it said

“This avi file was not prepared for sequential reading, the alternative “Avi Splitter” will now let the default one handle it”.

Someone told me to load the file in VirtualDub, which i did but it says

“Couldn’t locate decompressor for format DIV3 (Microsoft high speed mpeg-4 v3 (Hack: DIVX Low-Motion])
Virtual Dub requires a Video for windows (VFW) compatible codec to decompress video. Directshow codecs, such as those used by Windows Media Player are not suitable."

I tried downloading the VFW codec...

What do i do now? Could someone help me please?