Blue screen and stop error again

Hello,
My little sister's DELL, OPTIPLEX 210L PC was reported to be restarting automatically. I took it used it for a whole week without the problem so I parked it down. Just yesterday I connected it and tried to power it on, in that process it gave me a blue screen with a message as;
STOP ERROR 0*0000007E(0*C0000006,0*80684A64,0*F88906E8,0*F88903E4
My worry is that after I removed the CD-ROM DRIVE AND DISKETTE DRIVE, the PC worked well and after some hours I reconnected the earlier mentioned drives and it still worked well till evening. i'm just so confused about what is happening 'cos the problem sometimes is detected and other times not. Kindly help resolve this problem please.