Similar situation - I have a work-issued 2010 Dell Latitude (2.53GHz C2D, 4GB RAM) laptop with WinXP Pro SP3. Trying to run just MS Office 2010, Outlook, IE & Chrome; occasionally Quicktime and Picasa. And rarely simultaneously. It's dog slow. I click on an icon in the task bar and wait for the program to launch - and wait, and wait. It eventually launches...
My 2008 iMac that had similar specs (2.8GHz C2D/4GB RAM) before I put in an SSD and 6GB RAM ran circles around my Dell doing similar tasks. I can not see me trying to use a 2008 Dell laptop for these business-related tasks.
It's not that the hardware breaks; it just gets soooooo sloooooow over the years.
And yes - I defrag, I run virus protection and firewall, I keep my HDD clean and over 20% free, I install all updates, blah blah blah. I'm not this young kid who doesn't know how to work on and maintain systems. I'm one of the most tech-saviest persons in my business and circle of friends that's NOT an IT person. I've been running dual platforms since 1991 and there is a major and obvious difference between the user experience on a WinTel box and on a Mac. Looking back over the years, it seemed that every time I bought/built a WinTel box, throughout its life I found myself in this ever-present routine of upgrading the gfx card, upgrading the CPU, adding RAM, etc., just to maintain my user experience that I had when I got it. With my Macs however, any time I did something to upgrade it (RAM, SSD, etc.), my user experience IMPROVED versus getting back to how it was when I bought/built the machine. Just my experience...
I am given my Dell laptop (which is replaced every 3 years as they just can't keep up with the demands that the incremental software updates put on them) for work, but I choose to buy an iMac and an MBA for my personal machines. It's as simple as that. Even my wife, who was a die-hard Windows user (from XP up through Win7) threw in the towel this year and got an MBA.
I know I'll get flack for this on here, as all of a sudden it seems to be in fashion to bash Apple products on the Apple message boards... I'm just relaying my (and many of my colleagues' and friends') experiences with different computing platforms over the years.