The RAM use isn't necessarily a problem. All modern operating systems (Windows, Mac OS X, and Linux) will automatically grab as much RAM as they can for caching purposes to improve system performance. In your case, the IGP on your CPU is reserving 512MB of your 2GB for itself, so you effectively only have 1.5GB of RAM. The OS will automatically release memory used for caching if needed by some other program. From the screenshot you posted, you only just booted the system so it's not necessarily out of the ordinary that your computer would have a lot of disk activity, especially on an A4 based system. That should settle down after a time.
However, on such a low end system you should make a point of limiting the number of programs you have running, making sure to use a lighter weight AV program and even go through the Black Viper "guide" to Windows Services and turn off the ones you aren't going to need. You can click on the name of each service to get a brief explanation of what it is and does so you if it's an optional service, you can turn it off if you're not going to use it.