Will QuickSell 2000 run on Windows 7/8/10?

No, the drivers for QS2000 are not plug-and-play compatible, plus QS2000 is not PCI compliant if you'd like to use integrated card processing.
You'll want to upgrade to Microsoft Dynamics RMS to run on Windows 7/8/10*.
No security dongle is required. RMS uses a license key on POS lanes PCs.
A conversion utility is included with RMS to migrate all your QS2000 data to the new platform.
Training time is minimal since basic operations and screen layouts are similar. There is a POS module for register functions and a Manager module for back office functions.

*The recommended platform for POS operation is Windows 7 Pro 32 bit to ensure 100% compatibility with all possible POS peripheral drivers, RMS add-ins, and integrated card processing including EMV support. Windows 8 and 10 will also work depending on your hardware and merchant processor.