older desktop wont boot

[RobertMacUser]

it turns on,
a display screen describing the graphics card comes on
then a black screen with a blinking text cursor. it stays there.
i leave it like that and sometimes it boots (i come back days later)
any suggestions? its about 5 or so years old, pentium 4 1.7ghz

i was having a problem with a Disk icon blinking on my mouse cursor; i replaced the power supply and this error has been resolved.

any suggestions?