If you are using High Definiton files a 45 minutes of mov. files may take up to 5 hours to render using a say Pentium 4 3.2GHz 800fbs with 2 GB Ram and 400GB of Hard Drive space,
You should defrag your hard drives before editing or Capture and Importing Quicktime mov, files not so mpeg2 of say a Canon High Definition HV20
Most SD Projects may take up to 3 hours depending on the computers power, you should close every other program down including the Firewall and disconnect the internet to play safe/. you should set you computer on selective start up. ie., close everything down except Premiere.
Please tell us about your Assets and your Project.
If SD material (and going to DVD, I'd assume so), then you might be interested in using Bill Gehrke's benchmarking test files and his spreadsheet. This will tell you where your system falls in the performance arena.
From that site, you can start to match up your system's specs., with those of others.
Harm Millard has done some excellent articles on how to optimize one's system (and also how to purchase and setup wisely). If you find that your system is not performing up to par with the test files vs others' systems, I strongly suggest that you read each one of those. He covers everything from CPU to HDD and also includes powersupplies. Great reading for anyone with equipment, or setup questions.