Hmmm, you *should* just be able to grab the data files from your PC, copy them to CD/flash pen drive, then copy them back again to the new install and do File (menu) > Open ... (menu option) > Outlook Data File (menu option). You can see where your current data files are stored by going to Tools (menu) > Options (menu option) > Mail Setup (tab) > Data Files (button) - they will have the file extension of ".pst", so probably Outlook.pst. For extra peace of mind, you can export the info you are most worried about losing using File (menu) > Import and Export ... (menu option) > Export to a file, you can then see everything you have exported as say an Excel spreadsheet.
If it is just to fix a problem with your PC though, you should be able to use the Windows Repair option on your Windows install disk and that will leave your data intact.
Were it me, I would consider adding a second hard drive (they're cheap as chips), doing your new install on that, then copying files across at my leisure (while also having a backup to return to should something unforeseen happen). If you're not sure about that, though, you might want to consider checking for a local PC technician (cheaper and less of a skill-lottery than PC World) and have them do it for the sake of peace of mind ...