Bad video

Hi. I've got two problems.
A: Why all of a sudden, has my videos video and audio gone stuttery? FS still works fine.
B: Why do I have to open ALL videos in VLC Media Player, then simultaneously play them in WMP to get correct contrast.
Also possibly of use: my cpu is almost constantly 100% occupied, even when playing low quality music (96kbps).
Thanks. This has been going on for about 6 months, just been two busy to fix!
A: Why all of a sudden, has my videos video and audio gone stuttery? FS still works fine.
B: Why do I have to open ALL videos in VLC Media Player, then simultaneously play them in WMP to get correct contrast.
Also possibly of use: my cpu is almost constantly 100% occupied, even when playing low quality music (96kbps).
Thanks. This has been going on for about 6 months, just been two busy to fix!