Lenovo T61 laptop

He probably meant something like the following, only that that one isn't meant for a T61 and I can't find another:

http://shop.lenovo.com/SEUILibrary/controller/e/web/LenovoPortal/en_US/catalog.workflow:item.detail?GroupID=38&Code=43N3412¤t-category-id=6D8E5191FB0B45CBB39F45EB5B2B986E&&hide_menu_area=yes

Although it is possible to install OS's like Vista or Windows 7, and many Linux Distro's to USB drives, it would be slow as you have USB2. You'd need to get a USB3 PCCard adapter and a USB3 external HD to get good speeds, and that combination wouldn't be cheap.

I think you are better off to just get an internal HD and just swap the disks when needed. That is usually easy enough. 2.5" HD's aren't expensive. The Link below shows you how to remove it:

http://support.lenovo.com/en_US/product-and-parts/detail.page?&LegacyDocID=MIGR-67743

You can probably also get the additional caddy material from lenovo so you don't have to swap these also every-time, and make sure with your company that there is no security in place that would prevent your disk from working inside the T61.

look here :  http://www.hard-drive-help.com/boot-usb-external-hard-drive.html

You can insert a secondary HDD anytime by removing the DVD RW drive & using an Ultraybay adaptor.  Just ask in the ThinkPad forums if you need further assistance:

http://forum.thinkpads.com/

[Ignore the random "y" in Ultrabay]

Last question, what HD would you recommend?  Would this be the normal 2.5 HD?

It will be SATA 2.5" I would think.  Not sure 'bout boot order though if you are planning to have a secondary OS...

A SATA 2.5" disk, just check the dimensions first for where you want to put the disk in (Ultraby or normal disk caddy). Some disks could be a bit too "fat".

I use a lenovo X220 with a dock station for it and i have the bay adapter rindi suggested. I also have one of these connected to my docking station so i can have multiple drives hooked to my tablet.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817707170