Can I upgrade from windows 7 32 bit to 64 bit?

[SSSid]

I installed Window 7 32 bit when I should have used the 64 bit version.
Can I now insert the 64 bit disc and simply install the 64 bit version, or does it have to be a clean install?
Maybe i should leave things as they are. I have 4GB of ram and unless i increase this i know 32 bit is ok, but are there other reasons i should go to 64 bit?
Thanks for your answers in advance.

[Buenchico]

Click on "Can I upgrade from a 32-bit version of Windows to a 64-bit version of Windows?" here:
http://windows.micros...ently-asked-questions

Chris

[galeck1947]

Unless you want to play games which are ram intensive I wouldn't bother as the normal user will find that 32 bit ok . 64 bit allows you to access more ram which you wil have to install, 32 bit will use about 3.8GB of ram but if you add a 2gb usb stick and engage Ready Boost it will handle your page file and free up your existing ram

[SSSid]

Thanks to you both.
I did try to install 64 bit version, but disc would not boot.
The computer just started windows as normal.
When i opened the disc and tried to run setup.exe, i got the message "This program is not compatible with your version of windows".
Either i'm doing something wrong or it's a one shot deal. Install the wrong version and your stuck with it!
I'm going with your advice Galeck, and sticking with 32 bit (until windows 8 comes out).