Gary, I regularly drop several images of that size on my Vegas timeline and have no crashing problems.
If it helps, I'm running a QX6700 quad core with 3 hard drives, one for the OS, one for captured files and one for edited projects.
Getting files from and rendering to your OS drive is just asking for trouble.
Hard drives are very cheap these days so, if you don't have at least two, make the investment.
The increased performance & reliability will make you glad you did.
Forget about DPI as it's a term that's relevant to print work, not video.
The size of the image in pixels is the only thing to worry about.
I have Photoshop but use a free app called
IrfanView as it does batch resizing very quickly.
The rule of thumb for images is to keep them no more than 2X your project size unless you're doing deep zooms.
For DV NTSC, this would be 1440 x 960.
The other thing that has been known to help a lot of folks is to switch the images from JPEG format to PNG as this is a format that Vegas really likes.
Once again, I use IrfanView for this purpose.
edit: I 've got Vegas Pro 9 installed on my computer but, due to the various bug reports, I'm waiting for an update before I'll consider using it.
Mike