Techniques for computer system recovery which remotely restore a default partition to a recent state even when an operating system is functioning abnormally. In an example embodiment, a service center computer establishes a first network connection to a monitored computer system. The service center computer configures the monitored computer system to boot from a bootable image file in the monitored computer system and reboots the monitored computer system into an alternate operating system environment of the bootable image file. The service center computer establishes a second network connection to the monitored computer system to restore a recent backup image of the default partition from a diagnostic partition to a default partition. The service center computer establishes a third network connection to the monitored computer system and reboots the monitored computer system to the default partition.