Changes in desktop after loging in - open files

If you're thinking is malware I would say it's possible, but most malware is typically designed to be stealthy and doesn't causes issues like you've described unless it's scareware in which case you would get something telling you you're infected and you can pay X $$s and it will be fixed.

More likely you just have a corrupt or temp profile loading.
From a powershell prompt run it should be something like C:\users\<username>. if it has temp in the path then your profile had an problem and Windows switched you to a temp profile (which often will look very different then your normal profile.