A lot of things, alone or in combination, can contribute to the problem you report.
Indeed, your connection may have gotten slower. Perhaps more users are on the cable/DSL/whatever circuit than before, or perhaps your service provider's equipment has degraded. While it's hard to see what's what, there are tests you can run to see where you stand, and also to establish a baseline, against which you can compare future test results to see if your connection is getting slower (or faster!). Our friends at Cnet offer such an test: http://reviews.cnet.com/internet-speed-test/
You state that your internet connection has gotten sluggish, but that might mask the fact that your whole computer may have gotten bogged down. Some program suppliers seem to assume that theirs is the only program you'll run on your computer, so they load it with all sorts of bells and whistles, many of which you may not need, but all of which consume processor capacity. Over the year in which you noticed the slowdown, it is possible that some of the programs (or web services) you've used, have done this.
In fairness to the programmers, it must be pointed out that software developers must keep pace with the hardware guys to ensure competitive viability, and new versions of, or updates to, old favorite programs are often released to take advantage of the latest thing. These New! Improved! programs are almost always larger than their predecessors. It can't be a surprise to you that a 5-year-old computer running Windows XP is not the "latest thing."
Short of moving to a place where the internet service provider is a speed demon, or scuttling your rig and springing for a new one, there are some steps you can take to enhance performance.
First, ensure that you're running the most up-to-date versions of your key programs, in particular, Windows and Internet Explorer. Hit the green Start button on your screen, the Help and Support, and under the Pick A Task heading hit the Windows Update.
Try running Internet Explore in "safe" mode. That will prevent most of the add-ons from firing up. See if things are faster. Do that by hitting "Start", then Run..., and then enter iexplore -extoff in the "Open" window. Look carefully at what comes up. There will be a procedure that allows you to tinker with the add-ons and maybe eliminate some that are bogging you down.
Lifting from Microsoft's help library:
"Add-ons, also known as ActiveX controls, browser extensions,
browser helper objects or toolbars, can improve your experience on a website by
enabling content such as high-quality animations. However, some add-ons can also
malfunction or display content that you don't want, such as pop-up ads.
When an add-on, such as a toolbar, is installed on your
computer, it becomes part of your browser and operating system. In some cases
these programs might contain spyware. In the worst case, a malfunctioning add-on
might affect the performance of your computer or cause problems accessing the
That means, by the way, that your ad blockers, spyware and virus vigilantes may be contributing to one problem while preventing another. Pick your poison.
It would also be a good idea to see if there are things affecting you computer overall, not just the internet part. This is easy to miss, since many programs -- word processors, spread sheets, and the like -- are pretty fast to begin with (you can't, for example, type faster than Word can absorb), and even if on of these programs "fast" speed gets cut in half, you wouldn't notice. But more data-intensive routines, like many graphic-laden web sites, are slow to begin with, and if they are impeded, you will surely notice.
Here are two things to look at:
1) Using the Start, Run, Open procedure, type in msconfig. When that opens up, go to the Startup tab. This shows you what routines are automatically invoked when your computer boots up.
2) Using the Control/Alt/Delete combination will bring up Windows' Task Manager. Go to the Processes tab. That will list everything that's running on your computer. You can sort the list by Mem Usage, to see what's claiming the greatest capacity.
That's the good news.
Unfortunately, you're going to have to do some experimenting to see what among these under-the-hood items you can safely eliminate without creating problems for yourself. That may require rebooting the system.
Back to the good news, however, is the ability to create a Restore Point before each experiment, so that if things go kablooyee, you can get back to the prior condition. (Start/Help and Support/System Restore)
Do you regularly back up your important files? That'd also be a good idea before you engage in any heavy-duty tinkering.