how do i make one big drive out of 3 small;l ones while p.c. running?

bluefishtrail wrote:

I take it that by "while p.c. running" you mean you want to merge your
partitions non-destructively. For this you will need third-party
partitioning software. I prefer Acronis Disk Director but there are
others. Back up your data first because Stuff Happens.

Malke