Hi,

Is it possible to change kernel version from 32bit to 64bit.

Last time I make mistake and I install 32 bit version on server with Intel Quad processor and there is not possible to allocate more then 4GB of memory. There is also not possible to recompile existed kernel with PAE

Can I upgrade this kernel without reinstalling everything?

Simple:
Can I download amd64 kernel on existing machine (recompile it etc) and when I restart it, this will work on amd64 kernel. And can I do it per internet (without go to datacenter and installing new version from CDROM)?

Thanks

PS. I use FreeBSD 6.2

Then you'd still have all 32 bit applications although you are using a 64 bit kernel. I don't see the point, not to mention that 32 bit emulation under FreeBSD is less than perfect.