I am having the same issue. I'm using a Fujitsu LifeBook laptop with:
Windows Vista Home Premium SP1
AMD Turion 64X x 2 Mobile Technology TL-62 2.10 Ghz
3 Gb DDR2-667Mhz SDRAM dual_channel memory module
ATI Radeon Xpress 1150 Graphics Card w/256 MB memeory
Built-in flat-panel TFT active matrix LCD display
250 Gb Fujitsu ATA HD
PD 7 Ultra v 7.0.2519 (just purchase a few weeks ago)
Even when I burn the slideshow to DVD, the jerky and choppy slideshow is totally unacceptable.
My project has 61 pictures, one song, fades between each picture and pan and zoom on each picture.
I have used PD 6 on this same laptop with much bigger slideshows and no problems detected. I have been pretty disappointed so far with PD 7. I'm also not happy with the fact that you can no longer add transitions in storyboard mode also, but my biggest complaint is the choppy previews and final render. If this can't be resolved, I will have to go back to PD 6.