World class strange one

Hello,
Have a two year old E machine desktop. Quit wanting to connect to the internet. Modem hardware and drivers OK.. Computer does the short beep deal. Tried the easy stuff new RAM checked cables etc. Computer turns on boots up Can play the games installed on the computer. (hearts freecell etc) When trying to go online says services not running. Opened run box typed services.msc All disabled. Set them all to auto and restarted. only some working.Tried all the tricks-disconnect from power supply and press power button restart etc Was able to run installed antimalware no issues. When I plug in flash drive and open my computer it does not see it. Keyboard and mouse work fine Have a dvd drive and 150 gig hard drive. Windows xp. Was a little old ladys computer so no porn viewing etc. Kind of stumped since it will play the installed games, boots up, and monitor works fine. Can leave machine on for hours and it does not shut down or crash. Just a short beep now and again Hate to toss it would love to fix. A trip to the computer guru costs about half a new one. This problem happened out of the blue, no power surges or brownouts. Wondering if the power supply is not powering everything equally? Whats the output voltage supposed to be? I admit I am stumped. In real life I am a licensed aircraft mechanic and I really hate it when the machine wins. Any body out there help and I will tell you how to fix an airplane free. Thanks