mkv x.264 3.95 gb file to mpg2,24 hours??

[times]

i have a movie in mkv x.264 around 3.95gb and it said it had like 2 mins left and the progress bar was at halfway,now it says 23 hours left.ive had it encoding already for 12 hours.

can it take this long? ive got a p4 3.0ghz pc single core.