Hi

we use a Primary standalone environment for global deployment, though some of the sites need only specific task sequences available for deployment and not all task sequence.

we use PXE with deployments to All unknown computers.

is there a way without having to add the computer to a specific OU and then start the deployment to just have different TS available in every site based on default gateway or something?

for example:
a technician from Canada boots new computer to PXE and sees: "Windows 7 for Canada"
a technician from USA boots new computer to PXE and sees: "Windows 7 for USA"

I know I can add a condition at the beginning of the TS. i'm talking about hiding it completely

and I know in a CAS environment there's "All Unknown computers" collection for each site.

any options in a standalone environment?

Why using different task sequences? What's the difference between them? 
OUs and PXE boot have nothing in common at all. 

Even if you have different requirements within the TS for different sites (different domains, or OU's etc...) why do you believe this requires different task sequences?

just call the task sequence windows 7.

Add a script step into the task sequence that detects the site/ip address/gateway and based on that set a task sequence variable.

so for a pseudo example:

If gateway = 10.10.0.254 then
    TSVariable = "Canada"
ElseIF gateway = 10.11.0.254 then
    TSVariable = "USA"
End If

you can then trigger and filter steps in the task sequence based on what value the task sequence variable is set to.

and I know in a CAS environment there's "All Unknown computers" collection for each site.

Actually, this is not correct and wouldn't be a possible solution anyway.

I concur with Torsten and Kriss; however, if there is some reason other reason why you feel you *must* have separate TSes (maybe because they are controlled by local entities), then you can use a pre-start command that displays a subset of possible TSes and then forces a specific TS to run. This requires a bit of coding and hard-coding in the script though and is more trouble than simply making the TS dynamic as suggested by the others.