Internet Explorer 7.0 causing delay to load media files in Windows Media Player 9, 10 & 11?!

Hello,
I recently installed WinXP PRO Engish SP-2, with all the latest updates, including Internet Explorer 7.0.

After I installed IE 7.0, I noticed that when using Media Player, there was a delay of -3-4secs to load a media file (Avi,Mpeg,DivX, Xvid, OGG, MKV…). This happens when a video file is all ready being played in media player. If I choose another media file using Windows Explorer browser or Total Commander, it will take 3-4secs longer to start in MP. I have installed all the latest DivX, Xvid, FFdshow, AC3, plug-ins and the same problem occurs in Media Player 9, 10 & 11.
Media Player Classic however shows no problems or delays.

I can verify that that this lag is caused by IE 7.0, as I reinstalled WinXP PRO (Without installing IE 7.0 this time) and there was no delay when loading media files in Media Players 9, 10 or 11. I then reinstalled IE 7.0 (No other WinXP update) and the exact same problem occurred!

My system:
Core2 Duo 6600 @2.4GHZ
1GB DDR-2 Kingston HyperX 800MHZ
SeaGate 7200 SATAII 500GB
Asus P5B-E M/B
Asus GeForce 7950GT 512MB

The exact same problem occurred on a different rig with newly installed WinXP Pro SP-2, IE 7.0 & Media Player 11:
P4 3.2GHZ
512MB DDR-1
GigaByte M/B
80GB SATA HD

So, is this a known problem and is there a way round to fix it?
Or should I just stick to Internet Explorer 6.0, as it does not cause the above problem.

Thanks in advance.