Thanks joelito, you saved me from having to buy a new computer (for now).
Here's my tale, might help someone who still encounters similar:
Windows XP / Western Digital (WD) 2TB SATA HDD drive replacing (2) IDE (PATA) drives / MSI PM8M-V motherboard:
To begin, I installed the SATA drive with my IDE drives still active.
Initially, BIOS did not see the SATA drive.
So I did this:
"www.tomshardware.com: joelito18 09-15-2010 at 04:36:55 AM -- To recognise the SATA HDD in your MSI PM8M-V. First enter the bios menu, go to Integrated Peripherals, Then VIA on Chip IDE then on SATA mode Select IDE instead of RAID. There you go. Your SATA HDD will now work like a IDE and it will now be recognised as IDE."
Still, Windows XP did not recognize the SATA drive (it did show up on BIOS and when using "DOS" utilities). Checked XP's Device Manager and saw a RAID Controller with a warning message that the device was not usable. I let Windows select a driver for me, and the device became:
Standard Dual Channel PCI IDE Controller
XP could now see the drive, though I probably should have used the MSI drivers for SATA/RAID (assuming they exist).
Now I neded to copy my old HDDs as partitions to the SATA drive.
An old partition utility, "Partition Magic", and the "WD Data Lifeguard Tools" were mostly unhelpful and often counter-productive (Partition Magic apparently can't handle 2TB drives).
However, WD Data Lifeguard Tools did say that it updated Windows to completely work with 137GB or greater partitions.
So I tried the "GParted" (http://gparted.sourceforge.net/) partition utility, but it did not seem to get Boot partition activated correctly (MBR problem?).
Used WD Acronis True Image (www.wdc.com/advformat) for copying the Boot partition (C: drive).
((Remember, that the Boot Partition copy must have been made after you intalled the driver for the "RAID Controller". Otherwise, the new Boot partion won't boot because XP won't see the drive it is booting from.))
I did use GParted for the F: drive (my second PATA HDD) to copy to the SATA 2TB drive as a second Primary partition.
I removed my old IDE/PATA drives.
((BTW, there is a utility in the Administrative tools for XP called "Computer Management". If you run that, and go to the Storage section, Disk Management subsection, click on Disk Management. Your HDDs are displayed and you can make a Partition active there. Also you can assign a drive letter to your drive or partition.))
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Finally, I ran the WD Align utility for large WD "Advanced" drives, but it pronounced my drive was already OK.
Done.