Using Explorer from my laptop has been frustratingly slow any time network drives were visible in the left-hand pane. Any time I'd switch to a different program and switch back, it was a slow process (15-30 seconds) of Explorer enumerating each network drive, with a visible delay in the seconds range for each network drive. While researching network performance for another customer, I came across a way to dramatically reduce the amount of time Explorer takes to enumerate these drive letters. Apparently, when Explorer connects to a network resource, it searches the networked computer for scheduled tasks. You can turn this off by deleting the following registry key and rebooting: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\
After making that change Explorer now enumerates the drives in five seconds or so.