Windows 7: how to reinstall windows 7 on new hd

I want to put a new and large hd in aspire 5517 laptop. Can I use my original disk for this? Someone told me I would have to buy a new version.

Please see this tutorial: Clean Install Windows 7

and to answer your question, on the bottom of the laptop sometimes under the battery is what is called a COA sticker it should have your windows product key written on it, and so long as you are just reinstalling the same version of windows 7 as the one that originally came on the PC it should not be a problem.

COA sticker should look something like this:

When you say "original disc" are you talking about the one that came with the pc ? If yes, then you can use it and it should, I say should, auto activate it.

I have a label on bottom of laptop but it isn't completely readable. I don't have an original disk...just thought I did..I was told they don't give you them anymore....why is that? I don't think $150 for new one is fair

No, you don` have to pay for a new disc, you can download and burn it yourself, but you need your key to activate it, try harder to read it. Come on man

Yes, you can.

Everything you need is here to Clean Reinstall - Factory OEM Windows 7.

You own the OS which came with the laptop for it's life, to reinstall as often and in any way you want. But you need to be able to read the Product Key, so use a magnifying glass and decipher it now. If you're missing some digits MS Phone Activation sometimes can determine its authenticity other ways to activate it for you.

Even if you Clean Reinstall I would follow Wolfgang's advice below to save a Windows 7 or Macrium backup image externally so that you have another option in case you cannot get it activated due to unreadable COA.

If you cannot read the COA sticker, then you will have problems. In that case I suggest you make an image of your current system and transfer that to the new HDD. That is a safe way to do it.

I had written a tutorial on how to transfer an OS to a SSD. 95% of that would be the same in your case (except the alignment stuff). Maybe it helps you to do the job. SSD - Install and Transfer the Operating System