Hmm, 15 minutes is definitely not normal.
What kind of machine/OS is it? Quark 7 definitely runs better on the Mac Intel boxes than on older machines. (If it's a PC, I have no idea...Mac guy...) :-)
Have you thought about updating to 7.31 or 7.5?
Are you using a font management program to auto-activate fonts? Sometimes it can take a while to activate fonts, particularly if you have it set to activate fonts in EPS files contained in the document. I don't think it would be 15 minutes though. And that would only be a delay in opening a document, not just starting up Quark by itself.