I tried to install SP1 on my desktop numerous times and every time it failed at stage 3: always showing Stage 3 of 3 0%, then reboot, then failed again.
Submarine is correct - please search the forums and see the previous discussions for a variety of possible fixes and if you're still unable to resolve the issue, please post back, including detailing what attempts you have used to fix and the results of said attempts.
SanDisk Ultra SDSSDHII-960G-G25 960 GB SATA III SSD (System)
Crucial MX100 CT256MX100SSD1 256GB SATA III SSD (User Tree)
2 * Seagate Barracuda 7200.12 ST31000528AS 1TB 7200 RPM SATA II Mech. HD
Seagate ST1500DL001-9VT15L Barracuda 7200.12 1.5 TB S
PSU
Thermaltake Black Widow TX TR2 850W 80+ Bronze Semi-Mod ATX
Case
ThermalTake Level 10 GT (Black)
Cooling
Corsair H100 (CPU, dual 140 mm fans on radiator) + Air (2 *
Mouse
Logitech MX Master (shared)
Keyboard
Logitech G15 (gen 2)
Internet Speed
AT&T Lightspeed Gigabit duplex
Operating System
Sabayon Linux (current, weekly updates, 5.1.x kernel)
Manufacturer/Model
Lenovo ThinkPad E545
CPU
AMD A6-5350M APU
Motherboard
Lenovo
Memory
8 GB
Sound Card
Conextant 20671 SmartAudio HD
Monitor(s) Displays
Lenovo 15" Matte
Screen Resolution
1680 * 1050
Hard Drives
INTEL Cherryvill 520 Series SSDSC2CW180A 180 GB SSD