To transfer data from one PC to another you can copy the data over using portable storage media, network the two PCs or attach the old hard drive to your new system.
If your old PC happens to have a DVD burner, you'll need to burn two DVDs to copy all 7GB of your files. However, a CD burner will require ten discs as they generally only hold 700MB per disc. Portable USB memory keys come in fairly high-capacity models (512MB and 1GB), and provide an easy way to swap the files using copy and paste.
If you are feeling a little more adventurous, why not network the two PCs together. Both PCs will need network cards and chances are they will already have these installed -- look for a port at the back that looks slightly bigger than a telephone jack.
Next, you'll need a crossover Ethernet cable, which you should be able to pick up from your local Dick Smith or Tandy for about $5 - $10.
Connect the cable to both network cards and click Start -> Programs -> Accessories -> Communications -> Network Setup Wizard on the new computer. After going through a couple of steps on-screen, you'll be prompted to save the settings to floppy disk. Next, run the Network Setup Wizard on the old PC.
Once this is completed, you should be able to see the shared folders on the new PC through My Network Places to copy files into.
As for transferring e-mail, in Outlook Express, go to the File -> Export menu option on the old PC, follow the prompts then copy the resulting file using one of the methods above. Then click File -> Import in Outlook Express on the new PC and your messages should be moved over. You can also import/export mail settings, news settings and your address book.
There is also a "Files and Settings Transfer Wizard" in Start -> Programs -> Accessories -> System Tools that can be run -- do this first on the new PC -- to guide you through the copying process.
More information can be found on Microsoft's Web site.