How come I get a CPU overvoltage error after switching out my power supply?

Q: Hey, I just bought a DT Asus CM6870-us-3ab-rt Desktop, and it ran just fine, Then we tried putting a Rosewill Capstone 650W power supply in place of the generic one currently in place, upon startup, we got a Cpu Overvoltage error, which gives an option to go into an f1 menu, which we went through and tried a few tips, but it still stood red over the cpu voltage being at 2.040. We tried putting the old power supply back in and still the same error.

Any help you guys could give would be great, if it’s fixable. Here are system Details:
BrandASUSModelCM6870-US-3ABTypeBusiness Desktops & WorkstationsProcessorIntel Core i7-3770 3.4GHzProcessor Main Features64 bit Quad-Core ProcessorCache Per Processor8MB L3 CacheMemory16GB DDR3 1600MHzHard Drive2TB 5400RPMOptical Drive 124x DVD-RWGraphicsIntel HD Graphics 4000AudioALC892 8-channelEthernetGigabit EthernetPower Supply300WOperating SystemWindows 7 Home Premium 64-Bit

Motherboard
ChipsetIntel H77

CPU
CPU TypeIntel Core i7CPU Speed3770(3.40GHz)L3 Cache Per CPU8MBCPU Socket TypeLGA 1155CPU Main Features64 bit Quad-Core Processor

Graphics
GPU/VPU TypeIntel HD Graphics 4000Graphics InterfaceIntegrated video

Memory
Memory Capacity16GB DDR3Memory SpeedDDR3 1600

Hard Drive
HDD Capacity2TBHDD RPM5400rpm

Optical Drive
Optical Drive Type24x DVD-RW

Audio
Audio ChipsetHigh Definition Audio ALC892Audio Channels8 channels

Communications
LAN ChipsetIntegratedLAN Speed10/100/1000MbpsWLAN802.11b/g/n Wireless LAN

Front Panel Ports
Front USB2 x USB 3.0
2 x USB 2.0Front Audio Ports2Card Reader16-in-1 Card Reader

Back Panel Ports
Video Ports1 VGA, 1 HDMIRear USB2 x USB 3.0
4 x USB 2.0RJ451 portRear Audio Ports8 channel Audio I/O

Expansion
PCI Slots (Available/Total)0 x PCI
2 x PCI-e x1
2 x PCI-e x16