As far as I can tell the slowdown comes from two sources:
1. A buildup of useless data. When you surf the net, install trivial programs then uninstall them, or even find some files on your computer, all that information is stored in the windows registry. It doesn't go away either. Some of the more sophisticated uninstall programs remove all of the keys related to their software, however most of the software I've dealt with does not. The internet is a big factor too. Although you may religiously clean out your temporary internet files, the mass of cookies and the registry entries relating to them builds up. Programs respond more slowly because the data in the registry that they need to retrieve is hidden deeper and thus takes longer to get.
2. Hard disk re-organization. Now I didn't say "fragmentation" because even microsoft's disk defragmenter does a sufficient job of defragmenting your files, a major cause of slowdowns over time. What it does not do, however, is rearrange the physical placement of your files like they were when you first formatted your computer: all the files for each program all neatly stacked together in adjoining clusters. As FAT32 wreaks its havoc over your hard drives, .DLL, .EXE, and other important program files migrate away from their homes, slowing disk access much the way file fragmentation does. There actually is a way to fix this particular problem, however. Norton Utilities' Speed Disk has a special feature (it's turned off by default) that allows you to defragment your hard drive *and* move all of your files back to their home folders. I guarantee you'll see a signifigant speed improvement after that kind defragmenting and reordering.
As for the registry stuff I mentioned above, speed disk does not clean up your registry, and neither does ANY OTHER PROGRAM on the face of the planet. I have ruined my windows installation every single time I've used one of those accursed registry cleaners. Not to say you're not allowed to edit your own registry...in fact, I would suggest that after uninstalling some software that you open regedit and do some searches to make sure all the offending keys have been deleted. If you stay on top of it, you can stretch a windows installation almost 18 months.
And on a more opinionated slant, I have to agree that Microsoft is a money-grubbing market-driven producer of buggy, overpriced software. However, let's look at this objectively. First of all, Bill Gates is living the American Dream: starting a business and cultivating it into great success. Now whether or not that success was based on Apple...that's kind of beside the point (but not completely.) Either way, don't all operating systems have some bugs? Even the great linux (which I happen to use on my FTP server) has some bugs and security leaks. As for taking over, why not? Windows has become a standard. An upstart programmer can write an app for Windows 98 and can rest assured that 99% of the people he sells it to will have no trouble installing and running it. Because of this, how many of your favorite apps are available for linux? All the newest 3D games start out in Windows...they are only 'ported' to linux and other OSes much later down the road. The fact is, Windows may suck, but it's definately got its benefits. You just can't expect any OS to do everything. Linux makes a great, stable, server platform. The GUI and software availability for it is quite lacking, however. Windows is great as a GUI; it's easy to use, it sets a standard for other programs that run in it to improve productivity, and there is a gigantic software library available.
My point: Windows is great for what it was designed for: a GUI that is a worldwide standard. Other operating systems are also great for their respective reasons. Thus it makes no sense to be a staunch 'anti-microsoft' person, as you're denying yourself the benefits the OS has to offer by refusing to use it.
I run 3 computers in my home:
K6-II 400@450 running Win2k (serves my MP3s)
Dual PPro 200 running Linux Mandrake 7.2 (runs my website, FTP, IRC, Quake 3 servers)
T-bird 800@912 running Win98 (its the gaming/office/e-mail/internet/homework box!)
Yeah I know this was ridiculously long. But oh well.
-Skaven
Webmaster, Lunar Power
http://www.lunarpower.org
AOLIM: SkavenK