A. I have removed the Advance Power Management Support from the Device Manager by mistake.
1. If you removed it, it wasn't a mistake, and has nothing to do with your computer now beeping on boot. Most every computer will beep at least once which is normal, more is not normal but it's trying to tell you something.
2. The BIOS performs a power-on self-test (POST) (a built-in diagnostic program that checks system hardware to ensure that everything is present and functioning properly, before the BIOS begins the actual boot), a test which is used to ensure a system is functioning properly. When a problem is identified, the BIOS will normally produce an error message. In some cases, since a problem may be detected so early that the BIOS cannot even access the video card to print the message, a series of beeping pattern will be produced on the speaker to tell a user what the problem is. The exact meaning of the beep codes depends on the type and version of BIOS. A site to check for BIOS Post Codes is "BIOS Central" -- please note the box upper right-hand side identifiying the system BIOS used on the system -- this you must know.
Note: A single beep during the boot process -- usually right before the BIOS startup screen is displayed, is normal and does not indicate a failure as long as the boot process continues.
B. Tried to reboot with 98 bootdisc and also win 98 CD with no success.
With no success doesn't say anything. Using the correct Emergency Boot Disk/EBD boots on any computer will boot it to the MS-DOS prompt, but the computer BIOS must be set to allow such. It depends on the machine's capabilities whether it will boot from a CD however, which you say it is quite old. However, even booting with one or the other isn't going to allow you to proceed further by actually loading Windows that muct be read from the hard drive itself.
C. Bottom line is to ascertain what the beeps are telling you and to work on that reason/cause.
I have an old P133 computer with win 98. I have removed the Advance Power Management Support from the Device Manager by mistake.I lost the desktop and left with a blank screen and a repeating beep. Tried to reboot with 98 bootdisc and also win 98 CD with no success. I replaced the vga card as well, still blank screen and beep. Any suggestions of what to do next will be appreciated