Windows totally locking up every few minutes

Last night something horrific began happening that's continued today: Every few minutes the entire system locks up no matter what I happen to be doing at that moment: I get the hideous "Not Responding" message when I'm in Firefox, Word, and even in Windows Explorer..."OS (Not Responding). Between last night and right now, I've had to manually shut down the machine with the power button countless times; I have to shut it down and turn it on to be able to use my computer! Last week, I got a new PC with Windows 7 Professional 64 bit (from 32 bit on the old one).
I somehow created THREE User Account Control accounts in an effort to set up a Standard account like I had on the previous system (Ellen-PC), so I wouldn't have to have permission to do anything. But I still need permission on the UAC I logon to now which is Ellen Administrator. I've tried to change it to Standard account with no success.
Sorry for this long post, but this is happening no matter what I'm doing on my machine. You all know how horrible it is to have to do a total clean Windows install. When I upgraded from XP to Win 7, the 64 bit disk came with the 32 bit one I purchased to upgrade. Please let me have the benefit of your collective brilliant brains! ec

You don't want a Standard account if you don't want to have to ask permission to change things. You want an Administrator account. Enter Control Panel>User Accounts, select Manage other Accounts and delete all except Ellen that is clearly an Administrator account.

Next install Malwarebytes to run a Full Scan, if necessary from Safe Mode.

Next run SFC -SCANNOW Command, if necessary from System Recovery Options Command Line: SFC -SCANNOW Run in Command Prompt at Boot

Hopefully you've made your System Repair Disk in case you lose Win7 boot - if not make the disk now.

Thank you very much for your helpful response and suggestions, all of which I've followed. Things seem to be working fine now, and I want you to know how much I appreciate your help. Ellen

Glad to help. Ask any time.