installation:

-- download scite and install it (take the normal scite, not one that ships with ruby)
-- copy the texmf-context\context\data\scite\*.properties to c:\users\<youraccount>
-- copy the texmf-context\context\data\scite\*.lua to the place where scite has its own support files (wscite)
-- add the line "import context" to your user properties file (entry under menu Options)

running context:

-- add texmf-mswin\bin to your path

or

-- start scite from a cmd that also calls setuptex

spellchecking:

-- create a path for spell files and put spell files there (these are files with just words)
-- set the environment variable CTXSPELLPATH to this path