Black screen upon starting

Hello,

My old (about 4 year) HP-Compaq nw**37 (don't remember) was working perfectly until 3 months ago when it began to show a black screen at booting. The BIOS accesses the CD/DVD and HDD drive but then does nothing. The first time it happened I waited a while and rebooted again. It worked normally without any problem or error message. Then the same problem happened randomly at booting and each time I had to wait and reboot it after a while. But gradually the waiting time became longer and longer, and now I can not anymore start it. No change in original hardware and no software update since long time ago. However the CD/DVD drive showed some problem long time before this booting hanging. It seems to be related to a software problem (possibly on-board software). Once I reset the BIOS setup to default and it reduced the frequency of the problem for a while but it appeared again. Have any idea about the cause and a remedy ? I don't use this laptop anymore but it belongs to my previous job and I prefer to give it back in a working state. Thanks.

hz