Hi There,
I think I have got the jist of what you're trying to achieve.
What I would recommend is that you have links to Desktop PC's, Notebook & Tablets, Multimedia, Laptop, Netbook, Tablets / iPad directly from your homepage. The reason being that this will allow the search engines to crawl your webpages easier and the subcategory pages won't be so deep within the domain.
What I mean is that I would use either a drop down list, so that when the Notebook & Tablets is hovered over, the subcategories are then displayed below it. Alternatively, you could have a secondory naviagtion on the homepage, i.e. with an extensive drop-down list lower down or at the side of the webpage.
Great examples of this type of navigation can be found on: http://www.ebuyer.com or http://www.musicmatters.co.uk/shop.html (look at the secondary nav on the right for the Music Matters shop page.
I hope this helps.
Matt.