You are right at best you should see:
http://www.computing.net/windowsxp/wwwboard/forum/92590.html
200,000,000,000 Bytes/1024=195312500 KB 195312500 KB/1024=190734MB
190734 MB/1024=186.2 GB
Your WinXp was updated?
The disk was correctly identified in bios?
The 'largelba' registration entry was correct?
There was an MVP post that suggested a large disk that had been
formatted
prior to any 'largelba' fixes been undertaken could later cause disk
structure problems.
http://www.pcbanter.net/showthread/t-312226.html
see if your latge disk suport is enabled. Ensure latest MS updates
are on.
Lokie
To enable 48-bit LBA large-disk support in the registry:
Start Registry Editor (Regedt32.exe).
Locate and then click the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Atapi\Parameters
On the Edit menu, click Add Value, and then add the following registry
value:
Value name: EnableBigLba
Data type: REG_DWORD
Value data: 0x1
Quit Registry Editor.
For more details go here.
http://support.microsoft.com/default.aspx?scid=kb;EN-US;305098