When the RAM on a computer is mostly filled up, the computer takes the part of the RAM that has been left unused for the longest period of time and transfers it to the paging file on your Hard Drive. The Hard drive is much, much slower then your RAM, which means that your computer will slow down if you have too many programs open. However, this is solved by simply closing the program that you are not using in order to free up space in the RAM.
The only long term thing that can happen from using the paging file too much is that your hard drive will crash, and this requires, really, really bad abuse, (or an old SSD with no wear leveling, which 99% likely, you don't have) way worse then what you are doing here. A slow computer is not a long term result of having stuff in your paging file.
From what I have read about it, Windows Ready boost might help. Other things you can do include uninstalling programs you are not using, defragmenting you Hard Drive, or simply buying more RAM. RAM is basically the cheapest way to make your computer faster, these days, every computer should have at least 2GB of RAM. I personally prefer 4GB, which is the maximum that a 32-bit system can support.