When turning it on, PRESSING the POWER button, the hard DISK spins and the fans work, but the screen stays black.

Something must be corrupted in the bios... I don't remember how to reset the bios. Please help me.

p.s. I'm sorry, I don't remember what type of Lenovo desktop it is.Last night, while on the internet, the power dimmed... all of the lights became dimmer for a few seconds... and my computer reset and began booting up; after the lenovo logo appeared the lights dimmed again and my computer reset again; this dimming happened a third time and I realized that I needed to turn off my computer. I'm wondering if the bios isn't corrupted like I thought, but maybe could the problem be due to the cmos battery? Does repeated booting ruin cmos batteries?

Thanks for reading through this... just thinking. Maybe I just need to buy a new CMOS battery?I WOULD...

However it sounds like flakey power at your place is causing all the issues...If this helps... it is a Lenovo H50 Desktop PC, AMD A8 Quad-Core, 8GB Memory, 1TB Hard Drive, Upgraded to Windows 10.

@patio Yes, that is the cause of the issues. Though, that's never happened before and today has been like normal.Replace the battery ANYWAYS...Part # CR 2032...available anywhere.

Remove all power sources when doing so.Thank you patio! Will do that now.Keep us posted and good luck...With that new CR2032 battery my computer is working great again! Thank you so much for the help patio! Great News...