This is how I've learned to avoid re-inventing the wheel as a system builder:
If Windows is waiting for you to complete installation, cancel (reboot) it and make a full backup first (unless restore and OS discs are included). Label the disc "As Rec'd".
Once you complete installing Windows, make another full backup. Label it "Full Install". I would use DVD blanks and Ghost or Drive Image etc. (boot to DOS/Linux etc.; do NOT backup from inside Windows except possibly with newer versions of Ghost etc. which can manage that.)
*BEFORE* you go online for updated drivers and applications, Windows updates, etc., install a good firewall like ZoneAlarm. And a good real-time virus scanner. And a real-time spyware scanner. Your ISP, work, or school may provide you each of these. Now make an incremental backup. Label it "Security add-ons, Full Install".
Uninstall bloatware you will never use if you're sure of what you're doing, then make a full backup (a single DVD should still be able to backup your entire system at this point; if not, try a DL DVD or use multiple single layer discs, which the backup (imaging) software will span as if they are a single, giant DVD. Label it "Secure, de-bloat Full Install: Base System". You might instead de-bloat before adding security software - to be sure the system is still stable before installing security programs...
Now download those updates, install, and setup Windows to your preferences. Make another full backup and label it "Updated Base System"
From here on, you will need only make differential backups of new software you install to your "base" system, and any data you create, download, etc.
You *might* want to re-partition a huge hard drive into boot & data drives to make future defragmentations and backups easier (and disk access possibly faster). There are utilities for this process on Bart's.
Be sure to update your malware scanners every week or month and do deep system scans at least monthly (I do weekly) from a bootable disc such as one you can create from Bart's PE Builder Disc free program (http://nu2.nu). Most system utilities now come bundled with similar, bootable discs. Just be sure to enable booting to optical drives in your system bios (hit F8 while booting to enter CMOS/BIOS setup). If you merely scan for malware from within Windows, you've already lost the fight against some nasties that are built to hide themselves from detection by disguising themselves as Windows components which may not even show up in TaskManager.
If you only do one thing I mention above, PLEASE install a good firewall and virus scanner before going online...
BTW, you can also save yourself some grief the next time your system crashes (whether from software glitch or physical hardware failure -- both of which you can also check for from within Bart's disc) by making a final working clone/image of your hard drive to a *second* hard drive, which can then simply be swapped out for the "bad" drive when it crashes, then brought up to date with differential backup restorations.
This also gives you a great way to get back your old system if you upgrade to a new OS (such as Vista), then decide it's not ready for you yet. Just pop the cloned drive back into your system and you've got your old faithful setup again (so long as you did not clone the new OS to your clone/backup drive - always best to have two sets of backups; one of the current and one of the previous system just in case.) Newer imaging software will even allow you to run a second system from a compressed image of such a system stored in a large file on the same partition/hard drive as your current system (macs have enjoyed this luxury for years). VirtualPC can help with that flexible setup (free from MS, IIRC).
Enjoy your new PC!