My computer running Windows Vista Ultimate Service Pack 1 just developed this
problem. My computer began to grow really slow and started to crawl while I
was just on the internet browsing a few pages. I tried to ignore it, but
finally got tired and was going to restart, suddenly I noticed some
rectangular boxes (looked like inactive classic windows titlebars, blank, to
me) started to come up in rows above the taskbar. I could move them around
but I couldn't close them. I pulled up task manager with admin privileges
(took an effort) couldn't find any suspicious processes. Finally decided to
restart, but the computer froze. So I did a hard-restart.

The computer booted up, showed my the 'did not turn off properly' screen,
started up using normal settings. After logging into my user account, the
computer suddenly restarted (as if hard-reset). Tried again but same outcome.
Booted into safe mode, tried disabling all services and startup items, then
booted into normal windows, and turned out fine. Enabled all startup items,
restarted again, fine. Enabled all services, restarted, but computer resets
before Windows finishes loading all items and services. Finally I disabled
all services, started them one by one, restarting periodically and upon
starting 'Windows event log' computer resets. If I restart, it still resets
before windows becomes ready.

So I went into safe mode, enabled all services except event log and computer
works fine now. Could anybody suggest what is the problem?

Thanks in advance!