A new feature in BaseCamp (compare to MapSource) is the ability to directly use .img maps when your GPSr is connected to the computer in USB Mass Storage mode. This allows to use any .img maps without installing them. But there are two problems with this - first, access to the memory card is very slow this way, and second, you don't always want to plug your GPSr into your computer to use BaseCamp. Both problems can be solved by putting the memory card into a fast card reader and plugging that into your computer (or, for example, I can use my notebook's internal card reader). BaseCamp will see the removable device and not distinguish it from the real GPS. Basically any removable drive (memory card in a card reader, USB flash drive, but NOT an external hard drive) will be recognized by BaseCamp, just create a Garmin folder on that drive and put the maps in there. However to me it seems quite strange/stupid to require to have a memory card or a USB drive always connected to use the maps, so I researched a bit and found out a way to do it. First, I tried the Windows 7 built-in Virtual Hard Disk (VHD) feature. But unfortunately the virtual disk created is not recognized by BaseCamp as it's not marked as a removable drive but rather is a removable hard disk. Then, I found the solution. To make a virtual disk, I installed ImDisk Virtual Disk Driver (free): http://www.ltr-data.se/opencode.html/ Then I created a small 8Mb disk image, making sure I check the "removable media" checkbox, otherwise BaseCamp won't recognize it, which I mounted it as disk M. Formatted it as NTFS - it's not a problem for BaseCamp. Then I created a junction from M:Garmin pointing to D:mediagpsmaps - my hard disk where I've got the .img maps stored, using this command from the shell: mklink /j m:garmin d:mediagpsmaps Then I ran BaseCamp and voila - it's showing the maps from there. The reason for using the Junction instead of making a bigger virtual disk and just copying the maps over there is to avoid wasting disk space (or ending up with a virtual disk that doesn't fit all your maps at some point). Basically the virtual disk is almost empty and just links to another directory on my main hard disk. So there will be no need to grow or shrink the virtual disk image file. Unfortunately ImDisk doesn't offer the feature of remounting the virtual disk on system reboot, so I created a task in the Task Scheduler, that triggers after boot, and executes the remount command for my image: C:WindowsSystem32imdisk.exe -a -o rem -f D:mediagpsmapsmaps.imdisk -m M: There is another catch with using .img maps with BaseCamp. BaseCamp, and this this was done on purpose by Garmin, only shows Garmin original maps. But actually you can make any .img show up fine in BaseCamp, using JaVaWa Device Manager (free): http://www.javawa.nl/jdm_en.html I ran this program, selected my virtual disk M:, clicked on Manage Maps, then there's the list of maps on M:, and on some of them there is an icon "Visible in BaseCamp". The ones that don't have this icon, I selected and clicked the button on the toolbar "Toggle visible in BaseCamp". Started BaseCamp and all my maps are visible now. Not sure exactly what this does but it does write some changes to the map itself - if you copy this "visible" map to another removable drive or the GPS itself, BaseCamp will be able to see it from there as well. I'm just learning BaseCamp but it was not so easy to find this information, so I thought maybe it will be useful to somebody.