How to rename many files?

I've got Windows XP and about 30k files which need to be converted to .jpg format.

I've been having to rename each file individually, but it's taking ages. I've tried batch processing in Fireworks to jpeg, but since the file types are unknown, it didn't work...

Any suggestions?

 

I think it's called Tweak XP, its a program that can help you do that...

 

Thanks I couldn't find any programme based on those words? Do you mean Tweak Manager? (http://www.download.com/Tweak-Manager/3000-2094_4-10107938.html?tag=mncol&cdlPid=10196211) But how would it help with bulk changes. All the file names are different for example:

- 140434_5675_jpgfe3875219f048a99b8d4456c3c3903de
- 140427_789_jpg6340daf83d6e8b75e0e6a2c2b3419439

 

what's the current file names and what will be the new file names ? can you pls give some more details ?

 

The file names look like this:

- 140434_5675_jpgfe3875219f048a99b8d4456c3c3903de (no file extension)

and all need to change to .jpg format

 

open a command window, go to the directory where the files are and type:
ren *. *.jpg

and it will put .jpg after each file, keeping the rest of the filename

 

thanks, this works great!