How to lock my xbox 360 - Microsoft Xbox 360 Console

Error C800-0036 occurs when downloading an update to your Xbox 360 console. This may mean that there's a lock on your Xbox Live account. If your Xbox 360 console has been tampered with or modified, it can no longer connect to Xbox Live, install software updates or play new games that require a console software update.

see below:

https://support.xbox.com/en-US/xbox-360/security/forgotten-parental-controls-pass-code

open up xbox take battery out of xbox for few min. put it back in.

it could be the disk drive but are you sure you're using the right regioned game?
Xbox 360 is highly region locked?

Sounds like a bad disc, look closely at it try cleaning or replacing disc

I’m happy to help further over the phone at https://www.6ya.com/expert/eric_ab7c09ec01841771

Looks like a corrupted CD .. try exchanging it.

ur graphics card in ur xbox is over heating or playing up u may need to change the x clamps or put thermal paste on the chips also u could try and flash ur hard drive

sorry to say it but this is probably just another SOB story related to the 360's crappy hardware that was made in china for about 1/10 of the price you paid for it. Try not to mess with your xbox anymore and try to send it in to microsoft before the damage gets worse. Hopefully your still under warranty. Please tell me how it works out.I am also having to struggle with Microsoft over problems like this.

there is a common occurrence of total failure in Xbox 360 the 'red ring of death', where three of the red lights on the console flash, and the console locks up. there is a recall and repair for the failure that extends to 3 years from purchase, many xbox 360 have been repaired more than once under this plan, my son's has.
http://support.microsoft.com/kb/907534?sd=xbox
MS will not repair the xbox if it has been opened they will suggest that the failure is caused by any modification, take photographs of the console before placing it in the shipper MS will send you for the repair, they will damage it, you will need proof
do not attempt repair yourself,
http://service.xbox.com/servicehome.aspx

THIS IS A OVER HEATING PROBLEM BEST WAY TO COMBAT THIS WITHOUT OPENING 360 BUY A 360 INTERCOLLER FROM YOUR NEARIEST BLOCKBUSTERS PRICED AT AROUND £17.00