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I see only 2T from a 4T disk

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I had XP with a HD of 4T. maybe i formatted, i don't remember, i think not. it worked fine and i saw 2T.

Now dual boot 8.1+XP and still only 2T. it sees, though, 4G RAM.

It says x64 operating system, x64 based processor (old motherboard with i5).

How do i know if the computer really works on 64 bit?

Are motherboards and RAM's manufactured at x32 or x64, or does it depend only on the OS and CPU?

Do i have to format the HD to 4T, and can XP use it?


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32 bit or 64 bit is irrelevant when it comes to size accessible on disk.

A disk that has been partitioned as MBR won't normally allow to access anything beyond the 2.2 TB limit, this limit is not in the processor or OS bit width but rather in the partitioning scheme.

To access the whole 4 TB you will need to re-partition the disk as GPT, but then XP won't be able anymore to access it, though third party tools exist for working around the issue.

Anyway, the disk won't ever be bootable in XP, and it will only be bootable in 8.1 IF you have a UEFI firmware (as opposed to BIOS).

Again there are solutions (actually more workarounds than solutions) for these problems, but they tend to be complex to implement and to mantain.

No offence intended of course :), but - from your questions - you do not appear to have (at the moment) the knowledge and experience to apply them.

Briefly, it is possible on a 4 TB disk to create two partitions each one slightly smaller than 2 TB keeping the MBR partitioning scheme, then 8.1 should be able to access both of them whilst XP will only be able to access the first one, but the procedure is manual and prone to errors/issues, If you want I can assist you but you have to be aware that the whole stuff is at an "advanced" level.


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Yes please, advise how and where can i learn to do this (4T to XP & 8.1), and in general is there a good source of learning

I also want to buy a PCIe adapter for NVMe, in order to load Win on that, but i don't know if i can use a M.2 PCIe SSD or SATA SSD

I understand SATA uses PCIe, and i have them both, what are the pro's and con's for SSD?

My motherboard has BIOS, will i be able to boot from PCIe SSD, or should i buy SATA SSD, and if so, why, if at all, it's beeter to use a PCIe (x16?) adapter instead of a simple SATA SSD with the direct cable attachment

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Personally I wouldn't bother with NVME (it is actually faster but it is way more epensive and I don't think it would give any advantage, at least on XP, while sure it will be a nightmare with drivers) a simpler SATA SSD should be more than enough. 

Which (EXACT) make/model of motherboard do you have?

About making the second partition on the 4 TB disk, start by reading this thread:


even if you do not (yet) understand something it will give you some primer on the procedures involved.

In a nutshell we need to:
1) check the current partitioning scheme (with the actual data in the MBR, i.e. exact to the byte)
2) verify that the current partition and volume are fine and if needed resize them (shrink them a little bit) so that the second partition can begin before the 2.2 TB limit
3) create manually a second partition strating just before the limit and extending to the max possible size
4) verify that this second partition is seen correctly by the windows 8.1
5) verify how this second partition is seen in XP (very, very likely it won't ever - even if seen correctly - be accessible from XP)
6) format this second partition from 8.1 (to a NTFS volume)
7) re-check how this second volume is seen in XP (very, very likely it will not be seen "properly" and even if it is attempting to access it from XP might corrupt it, so probably it will be needed to remove drive letter assignment to it)
8) check the this seconf voluem operates correctly from 8.1


Edited by jaclaz
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I didn't read your reply because i have a problem:

I have overwritten 8.1 with Win 7 that i backed up before, but the dual boot menu disappeared, now i can't boot to XP.

Win 7 just boots without giving the option to select, as was before 8.1

Do i have to use EasyBCD, and how? and if i will want to install a third OS, how can i add to the menu?


Now that i have calmed down by writing to you, i can go and read your explanation... Thanks

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11 hours ago, Karol said:

Do i have to use EasyBCD, and how? and if i will want to install a third OS, how can i add to the menu?

Naah, leave EasyBCD alone.

Get instead BootIce if you want a GUI tool:


But you can fix the issue with BCDEDIT just fine, *like*:

Check (you will need to set the system to show in Explorer hidden and system files) that you have in root of C: the files:

Then recreate an entry in the BCD for ntldr as in the above.

With - select the BCD tab, then EasyMode, click Add, select "New Windows XP/2003 entry" and select the right disk and the C:\ partition on the right side of the window, and finally click "Save current system", have a look at this tutorial:

the relevant part starts around 7:53


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21 hours ago, Karol said:

I also want to buy a PCIe adapter for NVMe, in order to load Win on that, but i don't know if i can use a M.2 PCIe SSD or SATA SSD

Depends on what PCIe adapter you buy. Some support M.2 SATA SSDs and some don't.

Here is one adapter that supports both. If you are using an M.2 SATA SSD, find an adapter similar to the one I linked that is available where you live.

Here is one that only supports M.2 PCIe SSDs. Make sure to check the product page and buy the right adapter.

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