Hi there Firoz Khan
Thanks for posting on QandA platform
I dont think you can, directly increase the size of an existing data disk by using space from a newly created data disk. but, you can use both disks together in a spanned volume or storage pool.
On your Windows VM, open Disk Management.
Right-click the new disk (100 GB) and initialize it, Right-click on the existing disk (1024 GB) and select "Extend Volume".
now add the new disk to create a spanned volume.
This process will combine the space from both disks into a single logical volume.
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If this helps kindly accept the answer thanks much.