You haven't told us anything about your output files. Please advise the:
Composition resolution & framerate (ie 720x576 PAL, 25fps)
Output file type and codec (ie Quicktime Animation)
File duration and size (ie 30 secs, 1.2Gb)
It sounds like you're rendering files that are lossless or uncompressed, but your hard drive is not capable of playing files that are so large - thus, playback stutters as the drive struggles to read the data quickly enough. If that's the case, your renders are probably fine, just not playing smooothly. Try converting your render to a more appropriate format (like Quicktime H.264, PhotoJPEG, or even DV) for preview purposes.
Sorry well i did a test it was at 640 x 480 at 16 fps. The output file is .avi. and it was a 1 30 min file that is 2 gig.
And ok thankyou for that ill have a try later
As Andrew said - uncompressed files based on the default Lossless module always stutter in one way or the other. Your info seems to confirm that. For desktop playback, e.g. a WMV file would be much mure appropriate. If you want to further process your video in another program, your uncompressed file is of course okay, but you may consider other options like Quicktime Animation or PNG to reduce file size. And of course check the files in the target program then, not just on your desktop. Even those losslessly compressed formats will not play smoothly under any condition.