WINCEROOT is not set or is invalid

I build WinCE image successfully after following the build steps after
loading mini2440 BSP and SDK.

However a little later when I tried to load
F:\WINCE600\OSDesigns\Mini2440\Mini2440.sln, the VS5000 gives error:

The global default tree (WINCEROOT) has not been set or is invalid.

When tried to set the same through Tools>Options>Platform Builder for CE>
OS Design and Build 6.0>Default OS build tree (WINCEROOT) as F:\WINCE600,
it gives error:

The specified default build tree "F:\WINCE600" is not valid.

Also tried setting the environment variable as 

set _WINCEROOT F:\WINCE600 from command line as well as from
MyComputer>Properties.....

I donot get the project loaded.

Please help how to resolve this. Thanks in advance.

SatK

The specified default build tree "F:\WINCE600" is not vali
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 Set _WINCEROOT lode PB6.0 true path for you.