Your computer has many types of resources. They include the CPU, video card, hard drive, and memory. In most cases, the term "system resources" is used to refer to how much memory, or RAM, your computer has available.
For example, if you have 1.0 GB (1024 MB) of RAM installed on your machine, then you have a total of 1024 MB of system resources. However, as soon as your computer boots up, it loads the operating system into the RAM. This means some of your computer's resources are always being used by the operating system. Other programs and utilities that are running on your machine also use your computer's memory. If your operating system uses 300 MB of RAM and your active programs are using 200 MB, then you would have 524 MB of "available system resources." To increase your available system resources, you can close active programs or increase your total system resources by adding more RAM.
System resources can also refer to what software is installed on your machine. This includes the programs, utilities, fonts, updates, and other software that is installed on your hard drive. For example, if a file installed with a certain program is accidentally removed, the program may fail to open. The error message may read, "The program could not be opened because the necessary resources were not found."
As you can see, the term "system resources" can be a bit ambiguous. Just remember that while it usually refers to your computer's memory, it can be used to describe other hardware or software as well.