reinstalled Cubase and piano, cello, violin do not sound authentic

Not long ago, I had to erase my hardrive along with Cubase Artist 9, which was working nicely for the last year. I went to the Steinberg website and downloaded and installed the latest Cubase Artist 9 software onto my Dell Inspiron Corei5 laptop with 8 GB RAM and 1TB hardrive and Windows 10. The installation appeared to go fine. But when I go to All Media and select Piano samples, the only ones I get are the samples with plug-ins like Prologue, Mystic and Spector. The Grand Piano sample with Media Type Vst Preset and Plug in Prologue loads, but does not sound like a piano. It sounds more like a synthesizer. I have the same issue with the cello and flute samples using the Vst Plugin and Prologue. The samples do not sound authentic. They sound like a processed cello or a processed flute. This was not the case before I had to erase the hardrive. As before erasing the hardrive, I am using the Realtek Asio audio driver. I also downloaded the latest software update but there was no improvement in sound. Any ideas? Thanks.