Redmine

Hi, we are using redmine version 2.3.2 stable. I want to upgrade redmine to version 2.6, there is a solution for linux based systems but i can't found any information about windows based systems. Our redmine working on windows server 2012. How can i upgrade my redmine version ?

Not: I installed a new redmine (version 2.6) to another server(I am using bitnami setups). I tried to copy database tables on new installation of redmine version 2.6, everythings looks fine but some issues getting 500 internal server error. Sorry my poor english. Thanks.

Issue error (Just one projects issues getting this error)

Started GET "/redmine/issues/49" for 127.0.0.1 at 2015-01-12 10:06:15 +0200
Processing by IssuesController#show as HTML
Parameters: {"id"=>"49"}
Current user: yphit (id=12)
Rendered issues/_action_menu.html.erb (15.6ms)
Rendered issues/show.html.erb within layouts/base (46.9ms)
Completed 500 Internal Server Error in 156.2ms

ActionView::Template::Error (undefined method `name' for nil:NilClass):
34: <table class="attributes">
35: <%= issue_fields_rows do |rows|
36: rows.left l(:field_status), h(@issue.status.name), :class => 'status'
37: rows.left l(:field_priority), h(@issue.priority.name), :class => 'priority'
38:
39: unless @issue.disabled_core_fields.include?('assigned_to_id')
40: rows.left l(:field_assigned_to), avatar(@issue.assigned_to, :size => "14").to_s.html_safe + (@issue.assigned_to ? link_to_user(@issue.assigned_to) : "-"), :class => 'assigned-to'
app/views/issues/show.html.erb:37:in `block in app_views_issues_show_html_erb__440650712_56277192'
app/helpers/issues_helper.rb:158:in `issue_fields_rows'
app/views/issues/show.html.erb:35:in `_app_views_issues_show_html_erb___440650712_56277192'
app/controllers/issues_controller.rb:128:in `block (2 levels) in show'
app/controllers/issues_controller.rb:125:in `show'