You can use the workstation as a proxy. If all you want to do is transfer files between your laptop and the server I'd try to find another way to do this. If you use the workstation as a proxy then
- you have to set it up (a bit complicated).
- you have to maintain it (something will stop working;).
- unless you're very careful, you may leave your workstation (and potentially the server) vulnerable to exploits.
- you won't get optimal routing of traffic from your laptop to the server.
- you're unnecessarily using your workstation's bandwidth.
- even if you've set everything up perfectly, and you have access to the web server, the IP address whitelist hasn't really guaranteed you anything security-wise because FTP is an inherently unsafe protocol.
So I'd really try to go for another solution. What you really want IMHO is something with encryption and authentication. Is there any chance you could use a secure file transfer protocol? Choices include
These would pretty much just work, give you security, and not use your workstation. Can you give more details about the server? What are you allowed to do on it? Do you have SSH access? Can you contact its admin?
Using your workstation as a proxy
I don't know if Win7 has a proxy service built-in that you can use. My experience with Windows leads me to think that it would only be available with server editions (MS gotta make money somehow;) as it's really a server task. You can use a free piece of software such as Squid. I understand it supports authentication and encryption. Quick search reveals Freeproxy which might also work; there are others out there too.
There was a Lifehacker story that talked about installing a web-based proxy on a home web-server. That might be easier to set up but a) it might only be for HTTP, and b) more importantly you have to set up a web serving environment securely.