Thinkpad T60 vs a Desktop

Hello,

In my workplace I have a decent desktop (3Ghz dual core, 2GB RAM). I mostly work with the common office applications, though sometimes I do have to work with some heavy files (like a particular 500MB Access file and some 10MB-40MB Excels). Those heavy file sometimes overtax my PC and I occasionally find myself waiting 15-20 minutes for a query to run and sometimes, refershing a pivot in Excel can take like 5 minutes. (I know that MS Office probably isn't the most efficient IT solution for such data volumes, but that's what we currently have. Also, I only work with the massive files a numbered amount of time every month)

Now, since I sometimes have to work from home, my bosses want to give me a laptop - a Lenovo Thinkpad T60 (with 2GB of RAM).

What I would like to know is how strongly I am going to feel the performance difference after I switch to the laptop?

One more thing I should mention is that at work I usually open the files directly from the server and not from the HD, so the LAN connection is much more of a bottleneck than the laptop's slow HD.

Thanks in advance.