I can't seem to locate the original post, but I downloaded that printer evaluation .tif file, the one named PrinterEvaluation{mumble}ProPhoto.tif

When I load it into Photoshop preparing to print a test image, it pops up a box saying that the embedded color profile does not match the RGB color space. Should I convert it to sRGB? Should I be working in sRGB? I've been using the defaults of the standard Photoshop 7.x install.

Thanks, gang. :)

You want to keep/use the embedded profile in Photoshop.