the easy way at least for me was to copy all the files i wanted to convert to dds to the dds utilities folder in my case

C:\Program Files\NVIDIA Corporation\DDS Utilities

then open nvDXT

START>NVIDIA Corporation>DDS Utilities>nvDXT

in command line you need to type the in "" but with out quotes
for DXT1 (color only)
"nvdxt -all -dxt1c"
for DXT1 (one bit alpha)
nvdxt -all -dxt1a
for DXT3
nvdxt -all -dxt3
for DXT5
nvdxt -all -dxt5

and then wait the last time i used it i converted 52 512 x 512 from tga to dds it only took a couple minutesi did use infraview to resize since i'm a GUI kinda guy and find command line a bit of a pain