I know that I have used 88% disk space and you should have under 75% used but I have been at 88% for a while now and the performance has only slowed down recently, there are no firmware updates available for my SSD. I did take a look in the BIOS and the SATA type is IDE instead of AHCI which could be the issue, however when I changed it to AHCI Windows refused to boot so I changed it back to IDE. Are you aware of any reason Windows would not boot?
Thanks