I had RC1 on my test machine,but as soon as the update of RC1 i.e. build 5728 released I thought it would be better if I go for a clean installation rather than a mere upgrade.So I did a clean install.The installation was smooth and took almost twenty five minutes to complete.I configured Media Center and after scanning through the signals when live TV launched it was just shocking.There was continuous freezing along with bullet sound as if a machine gun was firing at random.All the concerned drivers were updated.There was no such problem in RC1.

I was getting constant message "Display driver nvlddmkm stopped responding and has successfully recovered." My display driver was Nvidia Geforce FX 6200 LE PCI Express with 256 MB.I immediately uninstalled the driver and installed the latest driver for Vista from Nvidia's site.No help.I even tried to install the driver for XP in compatibility mode but that too failed.So finally I decided to remove  the exsisting PCI express card and tried with on board intel graphic card.And it worked like a charm.And windows experience index also now has a higher score than the earlier,

Now as we are approaching towards RTM still we have problems  with nvidia graphic card.It's not a good sign.

srinath wrote But,       I heard that NVidia Has Good Drivers for Windows XP and even Vista ! My system is running with Vista RC1, Media Center is perfectly running on my pc with ATI AGP. Why Build 5728 does't support the  NVidia  PCI card  ?

No idea.