Operating system Windows 10 (64-bit). I presently have IDE 1.8.6 installed on my desktop. I've gotten several notices telling me that 1.8.9 was available, so I downloaded arduino-1.8.9-windows.exe & clicked on it. Gave me guided procedure, including uninstall of 1.8.6. I followed all instructions, and the last thing it told me I had successfully installed 1.8.9. However, the headliner at the top of the window said I still had 1.8.6 installed.
Meanwhile, I successfully installed 1.8.9 on my new lap top, without a hitch. They are quite different in the way they provide sketch uploads with different error messages. Also, now my desk top with 1.8.6 still installed has stopped running my previously successful sketches, only my lap top with 1.8.9 allows me to use my sketches. Even though I have repeated the install three times on my desk top with the same results. Can I get some advise as to what I can try?