[install-guide] BZ#1175759 Fixed Windows checksum steps

[Zach Oglesby]

commit 860d2f8dfd3c0c768a60749f94c44bfc854f053b
Author: Zach Oglesby <zach at oglesby.co>
Date:   Sat Dec 20 22:07:57 2014 -0500

    BZ#1175759 Fixed Windows checksum steps

 en-US/Preparing_for_Installation.xml |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/en-US/Preparing_for_Installation.xml b/en-US/Preparing_for_Installation.xml
index 2ae9d3a..4fedcdf 100644
--- a/en-US/Preparing_for_Installation.xml
+++ b/en-US/Preparing_for_Installation.xml
@@ -105,7 +105,7 @@ Mode                LastWriteTime         Length  Name
               Calculate the downloaded image's checksum. This will take a while!
             </para>
             <screen>
-<command><prompt>></prompt> $download_checksum = [System.BitConverter]::ToString($sha256.ComputeHash([System.IO.File]::ReadAllBytes($PWD\$image)))</command>
+<command><prompt>></prompt> $download_checksum = [System.BitConverter]::ToString($sha256.ComputeHash([System.IO.File]::ReadAllBytes("$PWD\$image")))</command>
              </screen>
             </step>
             <step>