I was installing ubuntu on pendrive and once finished I needed to run windows a bit, even though I chose erase and install ON THE PENDRIVE it altered my hdd boot sector

When I remove the ubu cd and pendrive it should only boot from hdd (windows) but it gives

Error: no such device : blablabla(numerbes and letters)
Grub rescue> _

If I place the pendrive inside it asks me whether to start windows or linux (windows works here)

I need to run windows without the pendrive, how can I remove grub from the hdd and also run ubuntu from the pendrive(once I remove grub from the hdd)

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THX ArK, your information help me do wonders! :)

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Now... it seems that without grub i can not boot the ubuntu from the pendrive anymore, blank screen and nothing loads(i did check the ubuntu with the grub from the hdd, and everything inside it worked perfectly (except the clock, it didnt find my local hour...) )

New problem: it seems that grub which is now on the pendrive is always asking me whether to boot from windows or ubuntu
F*ck of course i want to boot ubuntu otherwise i would stick the pen inside the computer