Rename a group of files using XP SP2

I have a group of 404 files that I want to rename. The files names all have a unique number as the last 3 char they are all 'jpg' files. There are several blank spaces in the name and I want to ftp them to my FTP site. Therefore I cannot have spaces. So I want to keep the last 3 char's and the jpg extension and add something in front of that without spaces. I have tries dos COPY command but can't get rid of all the spaces.
Here is and example:
"SVO Inventory 202.jpg "
I would like to rename it to "SVOINV202.jpg "
Now I have 404 files and want them all to be renamed the same way but I don't want to do each one individually,

 

Irfanview does that quite nicely.