I am seriously considering buying a laptop but I'm so out of touch with memory, speed, etc. that I need serious help!!!

What do I want to look for?
Also, I have no idea whether to get a Windows or a Mac? I've always used Windows and know nothing about Macs.
If I get a Mac, can I load the Windows based software that I already own onto the Mac?
Oh, and the Mac's are so much more expensive - are they worth it? Where can I find the best price on one?
I would really appreciate any advice...suggestions...whatever you can think of to help me in my search.
Thanks so much!
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