2.5 GB or RAM is a perfectly normal amount for Windows 7 to be using.

How much RAM does Windows 7 need to run smoothly?

1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor* 1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit) 16 GB available hard disk space (32-bit) or 20 GB (64-bit) DirectX 9 graphics device with WDDM 1.0 or higher driver.

What percentage of RAM usage is normal?

Steam, skype, open browsers everything draws space from your RAM. So make sure you don’t have too much running, when you want to find out about your IDLE usage of the RAM. 50% is fine, as you’re not using 90-100% then I can almost with no doubt tell you, that it won’t affect your performance in any way.