20 to 24 minutes?A) Plenty of time for the Processor (CPU) to overheat, and turn off. (BIOS turns it off)1) Heatsink fins clogged with 'Gunk'?(Dirt, dust, lint, hair, old socks {No}, banana peels {No)2) Processor fan, and computer case fans dirty?3) PROPERLY replace the Thermal Paste.Thermal Paste looses it's thermal conductivity properties over time, so don't think you can just stir it around a little bit, and everything will be fine. Properly clean, and use fresh, new Thermal Paste.
http://www.hardwaresecrets.com/article/274B) Check the Electrolytic Capacitors on the motherboard.(IF used. ECS motherboard? Since they are budget motherboards, there is a good chance Radial Aluminum Electrolytic Capacitors are used, and very few, if none at all; Solid Polymer Capacitors)
http://capacitorlab.com/visible-failures/index.htmBelieve the problem to be more heat (Overheat) related, though.[FOLLOW Anti-Static Procedures! ]For additional questions please post in a Comment.Also post the model number of the Elitegroup Computer System motherboard.Post back in a Comment/ReplyRegards,joecoolvette