I have had a gradual decline in Hard Disc and eventually it has given up the fight. I have replaced it with a new 256Gb SSD of the exact same spes/model. 

Problem: When I power up, with the BIOS set to read from DVD, so that I can reinstall Windows, the process appears to be running OK for a few seconds. I get the blue Microsoft flag up and the DVD is running. Suddenly the power shuts off. I try to power up again, but this time the power drops after a shorter period. I have new batteries, and I am connected to the mains. If I leave it for a while then the length that the computer stays powered increases again, to about 30 seconds, but then drops back each time I ty to power up. I have tried on battery and on mains, with and ithout the DVD attached.

When I had old Macs this seemed to happen quite frequently, and the CMOS battery needed to be replaced. The tell tale was that the internal clock was wrong. However, if I leave the laptop for a while, then power up and go to BIOS (F2) the internal clock is showing the correct time and date. I thought I would try to remove and reinstall the CMOS battery, but I can't see where it is. Any idea?

I would love to get my Vaio back up, so appreciate all suggestions