iMac erase hard drive but iMac won't start

You were not specific about which year but if it's a 2011 or earlier it's not too difficult. Here is a video for a 27" 2011 model.

https://eshop.macsales.com/installvideos/imac_mid27_2011_hd/ you can determine for yourself if you want to do it or not.

You will have to physically remove the drive if it will not start up. You can attempt to restart in the Recovery Partition by holding down the Command + R Keyes. Then open Disk Utility and format the drive. If it won’t start in Recovery then removing the drive is your only option.

fyi i'm on my hp desktop pc..

and i'm not able to do anything on mac as something must be corrupted after i wiped off my account because i no longer want to use..

although, ive tried to type my password in recovery mode but i cannot type anything.. did tried the command + R keys and it worked before but now it wont work.. when i do this, there's a flashing question mark at startup.. i tried everything with other keys and the spinning globe constantly pops up at startup where i cannot type my password.. help!

Then you have to remove the drive.

Here is the video for a 2007:

https://eshop.macsales.com/installvideos/imac_24_0708e09_hd/iMac7-1-24/