On my XPS 15 L521x (Windows 7) I was experiencing problems with programs getting corrupt and not working. This happened a few times and I would reinstall the programs and they would work correctly. The problem was completely random and was not affecting the same program each time. I though that is was possible the hard drive failing because I would also have to run check disk and problems would be found but corrected by chkdsk/F. This happened 4 times. Even though the laptop is still under warranty, I decide that I wanted to upgrade to a SSD drive anyway so I did not seek tech support. I order a Samsung SSD (540 512 gig) from Dell and installed using a clean boot into Windows 7. Installed all new drivers from Dell, programs and windows updates and the next day turned on the laptop and got "Operating System Not Installed". Frustrating, but thought that I might of done something wrong on the install of the SSD. Reformatted the SSD on the another clean install of Windows 7, reinstalled all drivers and programs and window updates. Laptop worked great for one week and now I got the "Operating System Not Installed" error again. Checked the BIOS and the SSD is recognized. I feel this might be related to my initial problem with programs getting randomly corrupt (windows Media Center, MS Office).