old win98 partititon interfering with Win 7/XP dual boot

gordo999 · 26 Oct 2015

I've had an XP installation on a desktop for years and I am trying to dual boot a new Win 7 install on a separate drive.

Years ago, my XP install started out as a win98 installation which I dual booted with XP. I no longer use the win98 partition but I need it as a place-holder for drive C:, since XP is on drive D:. It's only 4 gigs long.

I installed win 7 on a separate disk but I did not unplug the XP disk when I installed. The W7 boot-loader has set itself up as drive C: but lists the XP install as an older system. Obviously, with the XP MBR on the old drive C:, and with drive C: now in conflict with the new W7 drive C:, I can't boot into XP.

Put another way, on the computer management screen, my old drive C: has no drive letter now and I can't rename it to C: because W7 is using that letter. I tried renaming W7 to another drive letter but it wont take.

I could delete the W7 partition and start over but that would mean either repairing the old XP MBR on the old drive C:, or as someone else suggested, doing a full repair install of XP from the XP install disks. I already have the XP install disk integrated with the SP3 update.

Or, I could remove the old C: partition where the old W98 OS existed. Apparently that's a bit of a hassle and it might mean the existing partitions on the XP setup change their drive letter. I have no idea what would become of drive D: which holds the XP install.

Any suggestions besides upgrading to W10? Obviously I am running apps on XP that wont run well on W7.

AddRAM · 27 Oct 2015

You should not have to rename anything, the system you are in should always be C.

Reinstall Windows 7 again, this time unplug all other drives, then just set a default drive to boot and choose the other when you want with the one time boot menu key.

gordo999 · 28 Oct 2015

Thanks for input addram. I had already done what you advised, unplugging the existing XP disk and loading W7 on a separate disk.

Discovered some things along the way.

1)the drive upon which you install W7 has to be pre-formatted with a primary partition marked active. If you have an existing install on another disk, W7 will format the W7 disk for you when you reach that stage of the install. Without the formatted disk you can't get the install disk to boot because the system apparently needs to see a formatted disk with a partition before it will give the message to press any key to boot from CD.

I formatted the W7 drive after adding a primary partition while the XP disk was connected. Of course, you have to be mighty careful to format the right disk. I ran the W7 install disk from boot and when it got to the language window, pressed shift-F10 to get a prompt. Then used diskpart.

Also, when the W7 install begins, it needs to load files somewhere and if there is no formatted disk with a partition it can't load them anywhere, except to memory.

2)After installing W7 with the XP disk connected, W7 wrote to the C: drive of the XP install. Remember, my C: drive used to be a win98 partition and although it no longer has win98 on it, the MBR for XP is written on the first cylinder of the drive, which is C:

To clarify, my XP setup used to have win98 on the C: drive and XP on the D: drive. Even though w98 is long gone, and XP is on D:, the MBR for XP must be on the first cylinder of the drive, where w98 used to reside. The MBR cannot be on drive D: where the XP boot record is found.

I presume W7 saw itself as a partition related to the existing XP install and entered info related to itself on the XP C: drive. In other words, a Microsoft installation does not seem to be aware that the MBR for an OS located elsewhere may be on drive C with no OS on that drive.

To correct that, I tried fixmbr from diskpart on the XP C: drive. That would not allow me to boot into XP but I was able to do a repair install, which fixed the XP install.

3)when W7 is added to a drive where the XP install is on drive 0, partition2 (the old win98 C: drive is drive0, partition1), and the W7 drive is drive1, partition1, the original D: drive on the XP install is displaced to drive E:. The W7 install became drive D:

To fix that, I had to delete the W7 D: drive, (drive1, partition1) then use diskpart to rename the XP drive E: back to drive D:. Then the XP installer was happy to find the old XP install at it's normal place of drive D: and do a repair install.