HB - it just gives up at varying places in the procedure.
The most common is, without doubt, zero video, zero effort and a quick push of the power button on the case turns it off (just like a doorbell push).
Sometimes I will get zero video on screen (confirmed by yellow LED instead of green on monitor case) but it requires the four second hold down of the power button to shut it off.
If I do get the video output, then it could be anywhere along the process of;
Mobo confirmation,
CPU and Bios confirmation,
RAM count,
IDE drive detection (none),
SATA detection, (two optical, four HDD),
RAID configuration option,
Windows booting screen (small "horizontal tube" with coloured squares/dots running through it from left to right),
White cursor arrow on black screen,
Windows Vista logo, (small circle, like a golden ball)
Welcome screen (for password entry) - and audio chimes.
Desktop picture
Icon loading
Windows Sidebar Loading, and finally,
Small green "Vista doing something in general" spinning circle thing (used to be an hourglass).
If it gets to the end of that - it runs like a dream...auto skype login, Outlook opened (on command) and off we jolly well go.
Could freeze at literally *any* point in the process. Only recourse is to power down with the four second hold down of the main power button - then try again.
Time, temperature...all that stuff...seems to have no bearing on it. It's akin to "just catching it right" then it works if it wants to.
Mobo has 3 year warranty, PSU is 2 year, dunno about the RAM - but all components are 15 months old.