The mouse has a media mode. When you hold down the dpi button for 3 seconds it changes all of the functions, eg. the scroll wheel becomes volume control. It sounds like you accidentally switched to media mode so just switch back to standard mode by holding down the "dpi" button for 3 seconds.
I bought a silvercrest keyboard & mouse some months ago and I was highly delighted with it. Last week I changed my computer. Unfortuneately when I disposed of my old computer I ionadvertantly left the mouse USB still inserted and now cannot retreive it. Can anyone tell me where I can get a SilverCrest mouse USB ?
I'm in the same boat as you mate. My niece borrowed my USB receiver and her mother's keyboard, also a silvercrest but different model. She "lost" both somehow.
I hoped that I could use the remaining receiver and keyboard together as they are both 2.4 ghz and both silvercrest but to no avail. So if you have any joy or someone has a brainwave and posts a reply then I too would be landed.