Help App removal HELP!!!!!!

[Redtop89]

My son came to me the other day with his tablet and it had advert pop ups every few seconds. it would download new apps and repeatedly say apps had stopped working.
i have tried all day to rectify the problem, i have tried disabling the apps causing problems and forcing them to stop. i have stopped most adverts but i can not delete the apps. the launcher keeps changing and asking me to click on an option under device administrators. the app in question is called USBsecurity. it changes my homescreen icons etc like its a new skin and when i refuse it reverts back to the original launcher used by my tablet.
i have tried to factory reset the tablet and when setting up the tablet it continues to pop up with adverts.
i have tried rooting the device with various sources off the internet with no end product.
i have tried running security apps and they dont even find any problems they say the tablet is clean.
the only other option i have not done is flash the tablet back to its old updates and i dont know how to do that.

i have been on all day trying this and im about to have a fit of rage and smash it to pieces. please help.

 

[AP2FTW]

what kind of tablet is it? maybe try booting into safemode and see if you can get rid of them?

 

[Redtop89]

hi its is an asus memo pad me173x and i have tried safe mode. the apps that are causing most of the problems are still greyed out i cannot disable or uninstall them thanks.