Incorrect video time displayed

[real1ser]

Help
I have some MPEG-1 files on my machine which, when imported into a DVD authoring / encoding program, only plays a small percentage of the the whole file.
I know from watching these files previously on WMP that each file is approx. 25-30 mins long, but ever since i started trying to get them on to DVD, using various tools, each file is shown as being only 3 - 7 minutes long, ven now when viewed in WMP.
When the file is playing out in the media player (various), if i click on the progress bar to move it forward the time indicates that i am at 3 - 7 minutes when, in factm i know i am about 20 or so minutes into the clip.
The same thing happens when they are brought into my DVD authoring program or encoder (TMPGEnc). I carried on with the authoring and burn anyhow for a test and played it back - the result was - correct video for the first 3-6 minutes then BANG straight into the last minute.
I have just reinstalled XP - no difference.
Tools used = TMPGEnc plus - TEMPGenc DVD Author - Ulead DVD moviefactory3, Videostudio 7, DVD Workshop - Nero 6 (media player also) Pinnacle instant CD/DVD, Pinnacle 8 studio. All provide the same results.
Sorry to ramble on, but i couldnt think of a quick way to explain this - it also delays the moment of me trying to flush my PC down the toilet.
Please save my PC from drowning
Thanks for any help

[real1ser]

Ok, so i have scoured through this and many other forums and found out that this is nore than likely codec issues. So away i go to try and remove the codecs and reinstall just the ones i need