compaq v2000 laptop looses optical drive vanishes

compaq v2000 laptop , 3yrs old, xp home, turion 64 cpu, & standard stuff. 2
gb memory.

Sometimes when the system boots it doesn't detect the
optical drive, DVD-CD/RW. Sometimes it does. When it does, it works fine.

Any ideas what might cause this?

Bringing it up in safe mode has the same result, sometimes it's there, and
sometimes not.

Thanks,

Al