Is your project set to a PAL template?
Yes
Is your project audio set to 48KHZ?
44khz
Do you have any of the scopes windows open being updated live? No
What's your Preview RAM set to?
800
If your Preview window is set to Best/Full then you are asking a lot:
i use mainly good preview not much difference in fps between good and preview settings.
the clip is less than a one min and trying to work with a fps of around 5 is not much fun. i can only imagin how mind numbingly slow it would be on a more challenging project. i expect a reduction in fps but 5fps is very irritating.
would investing in a quad core improve the fps preview that much or would it not be a worth wile investment?
also am i right in thinking that a am2+ cpu will fit on an AM motherboard?

You've probably doen this but be sure your track opacity levels are at 100%. It's easy to nudge them to 99% by mistake and then Vegas has to render frames as it plays.

Rob Mack

When I start stacking tracks, I usually have to shrink my preview window down until I get full motion again. Sometimes it's only about 2 inches by 1 1/2 inches. Makes it hard to see if I have the audio sync'd right.
Oh yeah, I'm talking about SD video, NTSC and it might be better to get used to using 48Khz for audio for video. Vegas will convert to 44.1 automatically if you need to make a CD.
I use an AMD 64 X 2. 4200 and my preview is still set to 'Auto', but it gets down to almost a thumbnail, depending on how much I add. I hate it, but I'm used to it.
Just try shrinking the preview window just enough to get your playback fps back, but as you add FX, you will have to shrink it more
I know.....a crumby workaround
EDIT: corrected my preview post, above, from Best to Auto

forgive me - this is "slightly" off topic ... where do you see your FPS during preview? Is there a counter somewhere in vegas pro?

Right under the preview window, although I still haven't installed Vegas 8 yet, I doubt that would change.
It normally says 29.970, but it won't say anything until you playback something, then it's next to the window size, in 'Display'

im a little confused. when i preview with the window docked above the time line my fps is around 6, this is also the case when i hit the use 2nd monitor to prieview but if i un dock the preview window and move it to my 2nd monitor the fps increases alot.. when i undock the window it also increases the size of the prieview window is this normal that is should run alot better when it isundocked and manually moved onnto a 2nd screen?

You can undock the preview window and move it to the other screen, or leave it in the primary display (docked or undocked), and use DirectDraw Overlay to preview full screen on the secondary.

I have tried all options, and can't see any difference in terms of fps. When Vegas is capable of full speed playback (rarely - but this is another matter), it will do so regardless of the monitoring options.

You could be having data fragmentation issues ( are you playing back from a 2nd HDD? or are you running from the same drive as your OS? ).

Dave

I forgot about mentioning 'un-docking'.
That's when you can grab the edge of the preview window and stretch it bigger or smaller. Mine is un-docked and it's on my first screen and the rest of Vegas is on the 2nd screen. I don't think that matters.
I've had 4 video tracks and enough audio to bring the total up to 21 tracks and still was able to achieve full 29.970 in a tiny window, except for dissolves/fades and adding too many effects. Although I did notice certain camera tracks would slow to about 20 fps, for unknown reasons. I'd shrink my preview a little more and it would play.
I also play back my AVIs from a 2nd Hard drive.

OS is on c: vegas and stuff is on my usb E: drive.
i have no idea why my fps is better when i undock my preview and move it to my 2nd monitor. if i keep it docked in vegas or hit the full screen preview on 2nd monitor my fps drops to 6ish. moving my preview window to my 2nd monitor auto expands it a bit to take up around 6"
seems weird