I have a Dell Precision Tower 5810 that came with Win7 (about 18 months ago, more specs at the bottom). After about 6 months, I formatted the disk and installed Win10 from an MSDN subscription. Didn't touch the BIOS. All was working fine until recently, when I started having problems that led me to the decision to reinstall.
I just found a CD that I got with the PC, which is the Win10 installation CD (which I had forgotten about when I installed from my USB). On the back is a big red sticker that says "Please ensure that the BIOS setting is set to UEFI mode prior to installing Windows 10. For more information please visit http://www.dell.com/support/article/uk/en/ukdhs1/SLN300634"
Now I never did that when I installed Win10 a year ago, and it all worked fine (until recently, but that was a different story).
Having seen articles claiming that if you don't have UEFI enabled, Windows won't support disks larger than 2Tb (which seems odd as I have a 6Tb external drive on my machine that I use for backups, and it's been working fine), I decided to enable it before reinstalling.
However, with UEFI enabled, I couldn't boot the machine, not from the installation CD and not from a bootable USB that I created with the Media Creation Tool. When I disabled it, I could boot, and have installed Windows 10 successfully.
So, do I need to have UEFI enabled? If so, can I enable it now, or would I have to reinstall? If I have to reinstall, how do I boot from the USB to install?
OS: Win 10 Pro 64-
- Manufacturer/Model Number: Dell Precision 5810
- OS: Win 10 Pro 64-bit
- CPU: Intel(R) Xeon(R) CPU E5-1630 v3 @ 3.70GHz
- Motherboard: Dell 0HHV7N (SOCKET 1) version A00
- Memory: 40Gb
- Graphics Card: 2 x AMD FirePro W4100
- Screen Resolution: 4 monitors, one at 2560×1440, three at 1920×1080
- Hard Drives: 1Tb Samsung SSD and 1Tb WD HDD. Usually have a 6Tb Seagate external drive plugged in for backups