Need help wth partly dwonloadd .AVI file

dre ws a 4part avi file uploaded onto rapidshare which ws in a rar archieve,,,

i manged 2 download d 1st part of that file bt dan i dnt hv d links nw nd d only prblem i have is dat d extrctd file dat i get is of 700 mb whereas it hs nly 15 mins of vid on it nd d rest is all blank... is dre a way by wch i cn cut and remove d empty undwnloadd part of dat file??

please suggest me n utilty 4 d purpose..