I'm no expert, but shouldn't it be as simple as opening a new .txt document, pasting
[Version]
Signature="$Windows NT$"
MajorVersion=5
MinorVersion=1
BuildNumber=2600
[SetupData]
CatalogSubDir="\i386\Update"
[ProductCatalogsToInstall]
[SetupHotfixesToRun]
Q330994.exe /Q:A /R:N
Q819696.exe /Q /O /N /Z
KB824146.exe /Q /O /N /Z
qchain.exe
in (after editing it to your liking) and then saving it as update.bat?