For those that bought TopoUSA 4.0 on CD (7 CDs - 1 install and 6 data), there's a fairly easy way to convert them to DVD and have all the regions available to you at all times.
Basically, you need to make a new directory structure with a 'Data' directory and copy a couple files from each of the other CDs. I won't bore you with all the particulars, but will give you a list of what my DVD looks like once compiled:
$ ls -lgoR /mnt/cdrom//mnt/cdrom/:total 25dr-xr-xr-x 2 4096 Oct 1 12:25 Data-r-xr-xr-x 1 1633 Oct 1 11:15 T4CD01.adc-r-xr-xr-x 1 1638 Oct 1 11:32 T4CD02.adc-r-xr-xr-x 1 1650 Oct 1 12:15 T4CD03.adc-r-xr-xr-x 1 1645 Oct 1 12:24 T4CD04.adc-r-xr-xr-x 1 1638 Oct 1 12:20 T4CD05.adc-r-xr-xr-x 1 1906 Oct 1 12:21 T4CD06.adc-r-xr-xr-x 1 8487 Oct 1 11:32 T4_SeriesDefaults.xml/mnt/cdrom/Data:total 1440086-r-xr-xr-x 1 1883 Oct 1 11:14 vec_usa_01010202.ddm-r-xr-xr-x 1 247810027 Oct 1 11:15 Vec_USA_01010202.V-r-xr-xr-x 1 48145 Oct 1 11:15 Vec_USA_01010202.VI-r-xr-xr-x 1 1848 Oct 1 11:29 vec_usa_01020202.ddm-r-xr-xr-x 1 360997359 Oct 1 11:31 Vec_USA_01020202.V-r-xr-xr-x 1 71969 Oct 1 11:31 Vec_USA_01020202.VI-r-xr-xr-x 1 1858 Oct 1 12:16 vec_usa_01030202.ddm-r-xr-xr-x 1 291842092 Oct 1 12:17 Vec_USA_01030202.V-r-xr-xr-x 1 71269 Oct 1 12:17 Vec_USA_01030202.VI-r-xr-xr-x 1 1818 Oct 1 12:24 vec_usa_01040202.ddm-r-xr-xr-x 1 198625341 Oct 1 12:25 Vec_USA_01040202.V-r-xr-xr-x 1 49977 Oct 1 12:25 Vec_USA_01040202.VI-r-xr-xr-x 1 1828 Oct 1 12:20 vec_usa_01050202.ddm-r-xr-xr-x 1 167703489 Oct 1 12:21 Vec_USA_01050202.V-r-xr-xr-x 1 47293 Oct 1 12:21 Vec_USA_01050202.VI-r-xr-xr-x 1 1833 Oct 1 12:22 vec_usa_01060202.ddm-r-xr-xr-x 1 206992927 Oct 1 12:22 Vec_USA_01060202.V-r-xr-xr-x 1 372545 Oct 1 12:22 Vec_USA_01060202.VI