>I got on this road because I could not get SQL to install. I tried SQL Server and then SQL Express. When I downloaded SQL Express
>and tried to run it, I go "Not a valid Windows application". After tinkering I found out that my Laptop is 32 bit. So I then downloaded
>SQL Express 32 bit and it installed fine. But it got me thinking....

If you want to install a 64bit OS, I highly recommend win7 64bit instead of anything previous. It is very stable and runs most applications w/o issue.

That said, your machine must be 64bit compatible. Check the manufacturers' website. There is a compatibility checker on Microsoft.com as well. Make sure you have at least 4GIG RAM - the more the better. Most laptops prior to last year could handle no more than 4GIG max. Anything less I'd stick to a 32bit OS.

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>>>No, my question is more along the lines of is there any reason hardware-wise that I cannot uninstall 32 & reinstall 64? How do I know it will work?
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>>If the manufacturer says it will work and provides 64bit drivers, then it probably will work. Then the question arises, why do it?
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>>XP 64-bit was not the most compatible OS around even when you could find drivers (which was not easy).
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>>Vista (yecch!) and Win 7 have much broader driver support, and both have more compatibility options than XP.
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>>>>If you mean do an upgrade you can't do an upgrade install from any 32bit windows to 64bit as far as I know. Plus I would think it would be quite a pain in the neck because aren't all the drivers and such going to be different?
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>>>>>I have WinXP 32 Bit on my laptop. Can I install WinXP 64 bit?