regarding installation of Ubuntu rescuce remix and Ddrescue
 

i had download this software but i cundn't install it ..can some one guide me installation this software and help me recovering the lost data from external hardrive.please

This Ubuntu respin is not meant to be installed (which would overwrite data on your harddisk and defeat its purpose), it is meant to be used as a Live-CD/USB.
Please answer this questions, so that we can better help you with your issues:
1. How exactly did you loose the data (format, deleting a partition, ...)
2. Which type of data have you lost?

my external drive got corrupted and i just formatted and lost all data.
i have data mainly on office application and edited movies..i need to submit the movies as it is assigment
please help me..

You can use Photorec (which should be part of Ubuntu Rescue Remix) to try to recover your data. Here is a extensive HowTo that hopefully is helpful to you: http://www.cgsecurity.org/wiki/PhotoRec_Step_By_Step
I hope you know now how important it is to always have a backup of your valuable data.

when i finshed recovery i was to donate but am at place where we don't have visa card nor cerdit card..thats why can't save data..please help me with data recovery software

Photorec is a free program, it doesn't need a donation to use it. I never have used Ubuntu Rescue Remix, but I have used Photorec several times and I never had to donate anything just to recover some data. Normally I use grml (Debian based) or RIP-Linux (Slackware based) for that. May be you should try that.