Office 2010 Home and Student issue that has been plaguing me for months

My problem is, and has been since the first time I activated Office (purchased digital download on Amazon), that activations only last one day.

For example, if I haven't used Word in a long time and need to type something up, I'll open it and it will annoyingly ask me to activate it. I go over to Amazon and I find my activation key and paste it in.

Now, I've never actually tested how long it stays activated, I just know that I can close the program and use it again that day without reactivating. However, the next day I will have to paste the key in again.

Ironically, I bought my copy of Office because the previous copy I had was "unethical" and I felt bad and wanted a legitimate license. But this is a really annoying problem that I never faced with my illegal license. I'm pretty convinced having the illegitimate copy on my computer and not really uninstalling it correctly before activating my bought copy is what brought on this problem. Mistake, I know.

Anyways, I've reinstalled Office multiple times, and twice I've used an Office registry key remover tool to completely uninstall any remnants of Office from my computer. I've also tried to activate over the phone instead of over the internet.

Anyways, if anyone thinks they know what is wrong and can help me, any advice would be greatly appreciated.

I have a Dell Inspiron 580 running Windows 7 64 bit