Install Win XP 64 bit on Dell Dimension 8400

Only one disk shows in cmd prompt.

Yes, disks are RAID array, and running RAID (mirror).

Each disk is 150 GB, but windows shows only 150 GB totally.

Yes, when I tried ctrl+I, both disks are there.

"F1/F2 usually signals a misconfiguration of the BIOS (devices enabled with nothing connected, hardware errors, etc.).  If there is nothing in the BIOS showing as "unknown", then watch the POST screens very carefully for another message ... disk 1 not responding, fan failure, etc."

Watch the POST screens for ANY messages indicating problems (fans, disks, temps, chassis, etc.).

Boot to BIOS Setup (F2) and see if anything shows as "unknown".

If the above two things do not help, then start by disabling your floppy disk and/or your optical drive.  You said you don't have anything connected to SATA 1 - make sure it is OFF/DISABLED.

ok .. thanks so much !!!

Next problem is every restart I have to press F1 to continue. What would be the reason?

Yes, but you will have to rebuild (re-sync) disk B once you put it back in.  Although, you should have enough SATA ports to have all three connected at once - two in a RAID 1 and one as a non-RAID disk (but maybe you don't have enough power connections or data cables?).

Yes, I have cable facilities only for 2 disks.

Please let me know how rebuild (re-sync) disk B can be done.

yes, exactly.. the floppy disk was in Internal mode.. So I OFF it. Now no more F1 pressing. Great help  theflash1932.. !!!

One last thing. Since I have some data in another SATA disk (lets say SATA 1) which is not RAID is connected now by removing the Mirror Disk (lest sat SATA 2) which was in PC while installing OS and also it is in RAD. After I backup my data from SATA 1, I can connect SATA 2. Would this process effect SATA 2 later?

Let me explain again. I have 3 identical  SATA disks (say A, B, C). When I was installing OS,  A and B were connected. Since, by any chance, the system was configured as RAID1 (Mirror) [I have no idea how this happened], B is a mirror of A, as you said both have the same data for backup.

However there are some necessary data in disk C which was not connected to the PC while OS was installing. But when I replaced B by C after OS installed, I noticed that C is NOT RAID. But I can access its data without any problem.  After I get necessary data from C, I'm thinking of replace C by B. Then PC has the same hardware as original. Otherhand, I'm then safe if one hard disk dies.

But I'm wondering that this process would affect A and B (which are working as mirrors) or the system efficiency? Will they still work as mirrors?

I'm not sure I understand what you are asking or what you are trying to do.

If you had data on a disk and put it in a RAID array, then there is a better than good chance that the data will no longer be accessible ... is that what you are asking?

Glad to hear it :)

Great Help  theflash1932.. I would say YOU ARE THE MAN !!!

This is a awesome site with aw some people.

Now the problem is solved !!!