Hi Zacco1,
The above error could mean either there is an issue with the AC adapter or the system board?
To check further access BIOS (Tap F2 on start up,Dell logo) and look for AC adapter type.Does it show unknown or 65/90 watt?
If it shows "Unknown" you can try a different AC adapter(Original Dell AC adapter) and if it still shows "Unknown" then its an issue with the system board.
Regarding the system being slow the hardware diagnostics does not show any issue with the hardware so it may be software related.You may first try uninstalling your antivirus software and check if system works better/faster without it.
Also try updating BIOS on your system.Use this link to download: http://dell.to/177whI8
Note:While updating BIOS the AC adapter should be plugged in,battery should be adequately charged(more then 10%) and all external peripherals such as USB devices should be disconnected.Do not turn off system while the BIOS is getting updated.
