If you are using MS volume license there's no such problem, please ignore this instruction.
If you are using MS OEM license or single license, please do as bellow:
1, Diskless boot the main client PC, check if there is no Windows activate message, if ok shutdown this main PC.
2, Diskless boot the 2nd PC, if there's a message need to activate Windows, shutdown this client PC and enable super client in this client PC. Then Diskless boot and activate the Windows.
3, After activating the 2nd PC, shutdown this 2nd PC and turn off the super client.
4, Diskless boot the 1st and 2nd PC to check if there is no Windows activate message, if OK proceed to the 3rd client PC and do the same procedure as Step 2 and Step 3. Then diskless boot the 1st, 2nd and 3rd PC to check if OK or not.
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Attentions
As we know, you can use 1 Windows OEM license key in 3-5 client PC's, if there's an activate message just change the key using super client.
Please do not use super client update image in 2 or more client PC's at the same time, use super client in per PC only.