A way I just checked my RAM speed was going to task manager (via Ctrl+Alt+Del), clicking on the performance tab then memory. To the right of the "Memory" title in the memory tab should list the DDR type your RAM is. On the bottom right-hand side should be a table, where the supported RAM speed is listed, how many slots are occupied/being used, and much more information on your RAM. I hope this helps, as Windows 8.1 task manager looks near the same as that of Windows 10.