Running PC-Doctor DOS from USB drive: Solution

twistero · **Posted:** Mon May 28, 2012 5:34 am

So, to prepare for a upcoming troubleshooting session with my friend's X60, and for the general welfare of my own X60t, I want to boot the PC-Doctor DOS CD (1ety48ww, for T3x/T4x/T6x/R4x/R5x/R6x/X3x/X4x/X6x/A3x/G4x/G5x/Z6x) from a USB drive.

Attempt 1: Load the ISO via SYSLINUX and MEMDISK. The image will boot, but hangs randomly when extracting files to RAM.
Attempt 2: Load the ISO via GRUB4DOS. The image will not boot.
Attempt 3: Since the CD boots via harddisk emulation, I extracted the hard disk image file from the ISO (1ety48ww.ima). Although WinImage reads the contents of this image fine, it does not boot via GRUB4DOS either; GRUB4DOS complains about being unable to mount the drive.

Then, I opened the hard disk image with a hex editor. The first couple hundreds of bytes contains references to "Roxio CD/DVD-ROM Boot Loader v1.01". Some blank bytes follow, and at offset 0x00004000, strings like "IBM 7.1" and "FAT16" appeared. :twisted:

Solution: Using a hex editor, open up the hard disk image 1ety48ww.ima, and delete everything between the start of the file and offset 0x00004000. The image should start with:

Code:

Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00000000  EB 58 90 49 42 4D 20 20 37 2E 31 00 02 04 01 00  ëX.IBM  7.1.....
00000010  02 00 02 00 00 F8 85 00 20 00 40 00 20 00 00 00  .....ø…. .@. ...
00000020  4F 13 02 00 80 00 29 F5 12 4E 0A 44 52 49 56 45  O...€.)õ.N.DRIVE
00000030  2D 43 20 20 20 20 46 41 54 31 36 20 20 20 90 90  -C    FAT16   ..
00000040  90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90  ................

Then, boot this modified image (now a partition image instead of disk image) via GRUB4DOS. The relevant entry in my menu.lst reads:

Code:

title PC-Doctor for ThinkPad T3x/T4x/T6x/R4x/R5x/R6x/X3x/X4x/X6x/A3x/G4x/G5x/Z6x
map --mem /pcdoctor/short.ima (hd0,0)
map --hook
root (hd0,0)
chainloader +1

Notice the use of (hd0,0) instead of (hd0), since the image is only one partition, not an entire disk. Voila! It boots and runs perfectly.

Hope this helps someone. :mrgreen:

RealBlackStuff · **Posted:** Mon May 28, 2012 9:57 am

Have you seen this? http://www.911cd.net/forums/lofiversion ... 24021.html
They claim it works without modding the .ISO
BTW: how big is the data-volume of PC Doctor, would it fit on 64MB flashdrive?

twistero · **Posted:** Mon May 28, 2012 10:40 am

RealBlackStuff wrote:

Have you seen this? http://www.911cd.net/forums/lofiversion ... 24021.html
They claim it works without modding the .ISO

I did run into that post, but by then my tests have already shown their method doesn't work. Just to be sure, I tried it again just now. It still doesn't work, throwing an "Error 5: Partition table invalid or corrupt".

RealBlackStuff wrote:

BTW: how big is the data-volume of PC Doctor, would it fit on 64MB flashdrive?

The trimmed image file is 69,639,680 bytes or 66.4 MB, too large for a 64 MB flash drive. However, GRUB4DOS supports gzip'ed image files, and I managed to compress the image to 53.8 MB (56,498,218 bytes), which has a good chance of fitting on to a 64 MB drive.

Running PC-Doctor DOS from USB drive: Solution

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