blue screen of death?

Could simply be a sign that your hard drive is ready to take a dump. Back up any data or files you want to keep, burn them to a cd is the best way. Hard drives dont last forever, the disks are made of the same material that cassettes and vhs tapes are made of. The actual recording medium is called iron oxide or in laymens terms, rust particles! The average life of a hard drive is about 4 years althought it veries greatly in either direction. I have had them go sour in 3 months, I have also had some of them last for 8 years! It sounds to me like your drive is sometimes having trouble reading the boot.ini file....good luck!

I have seen this with a hard disk that is straring to go bad. Could be other things though... motherboard, memory, video, sound cards... I know, not much help.

It can't be software related if the Bios doesn't detect the hard drive on boot. 50% -50% between hard disk and motherboard....

Only two possibilities for the BSoD

1) Either your Windows is Corrupted

Solution : Reinstall Windows

2) Memory (RAM) is Faulty

Solution : Change your Memory

Try updating your computer- http://windowsupdate.microsoft.com/

Then (even if that works), run scan-disk (my computer-->right click C:/-->tools-->check now), to prevent that from happening again!