I have been in the ACT for a few months now and I must admit I have not found a computer store I’m happy with. Computer Fairs are very popular here and probably the reason its hard to find a real computer store. Most Sat and Sun you will find a fair on somewhere (check local media).
In Melbs or WA its not uncommon to find stores where you purchase through the front counter, then collect your goods from some massive where house out the back. Something I am yet to find in Canberra (help wanted).
HT in Fyshwick carries a range of stuff in stock. It’s pretty basic and pricy. Harvey Norman and Domain have big computer / technology sections. Stay away from HiMicro in Fyshwick tho. They have all but one blank CD in stock (let alone pc parts) and will charge you for the privilege of listening to them dribble rubbish.
My number 1 for PC stuff nowadays is EBay. If you do your research (like any good purchase) you can make some real savings. To be honest I very rarely use anything else. I try to choose Sydney based vendors for expensive (warranty) type stuff and international for everything else. I could go on for hours about the savings. Time and time again I have browsed the retail stores, playing them off against each other for a lower price. Then I check eBay and find the same item $50 cheaper - delivered to your door.