Windows 7 does its own disk defragmentation in the background. Even with Windows XP which requires manual defragmentation, from my own stopwatch tests, unless the hard disk is in a severely fragmented state where it is constantly above 90% capacity usage, defragmentation has very little realworld difference on fragmentation. Part of the reason is due to Windows XP/Vista/7's prefetch features which defrag and sort frequently used applications.
If you need a free HDD defrag tool, there are plenty out there, such as Smart Defrag and Defraggler.
For cleaning out junk files and the registry, it's hard to beat CCCleaner, also a freeware product.
As for drivers, I tend to stick with existing drivers unless I've a problem with one or see that the new driver has significant performance improvement. I've already had experience of updating a device driver only to result in an unstable computer, one time several years ago with an IDE driver that resulted in me having to reinstall the OS.
If you get a persistent pop-up like this or anything else claiming to fix a problem by purchasing a product, you've got a Malware problem.
Generally most pop-ups like these occur while browsing by displaying a large animated GIF or flash video to appear like a utility/scanner, so my advice to people is that if they get a pop-up like this, click Start -> Shutdown and Reboot. It's better to put up with a few minutes inconvenience rebooting the PC than trying to tackle a pop-up and actually ending up installing the malware, since the 'x', 'cancel', etc. buttons are usually fake.