I added a second hard drive (with DOS 6.20 on it) to my HP Pavilion 543x Windows XP Home machine with an external switch connecting to the "master" and "slave" pins of both the old (in "primary master" position on the cable) and new (in primary slave position on the cable) drives so the machine would cold-boot from either drive as selected by the switch. In other words, starting from an OFF machine: select switch, power on, boot either DOS or WXP. When want to use the other OS: shut off power (carefully in Windows, just hit power button in DOS), wait until machine stops, flip switch, hit power button, boot other OS.

Worked like a charm until I decided to try another method while in DOS: leave machine on, flip switch to WXP, hit CTRL-ALT-DELETE, booted DOS. WHOOPS! OK, back to first method: power off, leave switch in WXP position, power on, booted DOS AGAIN! Double WHOOPS!

The BIOS says the primary master is "none" (i.e., the WXP drive isn't recognized at all). However, PCCHECK.EXE says that that drive is perfectly OK. I'm guessing my experiment clobbered the master boot record on the WXP drive, and I'd appreciate suggestions on how to restore it so WXP will boot again.

--Myron A. Calhoun

Follow the instructions here: Sorry just being lazy why type the instructions for you when some other thoughtful person has already done it.

Fix MBR

Post back if you still have probs.