Regression test will be done when we got modified build

there we execute test cases to determine whether defects 
closed or not?

or checking 2 ensure that resolved bug has made any impact 
on the remaining part of code

Regression Testing is as discussed in above answer is done
after the first build release, and in regression testing we
test if the bugs that exited in the Build are actually fixed
or not, we also apply testcases for new requirements (if
any) to check if the system is working fine.

Regarding the regression testing procedure, it is same as
testing, we just re-run all those test that were previously
run, but this time we make sure that the test cases match
the new chnages, or new requirements that were not there in
the system.

Regreesion testing is nothing but whenever we find out the 
bug , it has to be fixed ,given to developers they will fix 
the bug , this is known as regression testing

Regression Testing-"Testing to ensure that introduction of 
new functionality has not affected existing functionality"

Whenever tester gets the next fixed build:
1)He tests for the Fixed Bugs.
2)Test the whole application to  check whether these fixes, 
have not introduced new bugs.
3)If there are some update in the application, then test 
cases need to be updated , and executed the same.

All of the above steps used, while doing regression testing.

Reexecution of testcases on modified form of build is 
called regression testing.

regression testing:when ever the bug is fixed from 
developement team we can verify whether the bug is fixed or 
not and their related functionality is also working fine or 
not.

Hi Pramod,
 i Agree with your answer. but a small confusion while 
doing regression we do execute all the test cases? or only 
few test cases which are related to particular bug??

The regression testing is conducted on modified build, as
soon as we get the modified build from the development team
we conduct testing on previously failed test and then passed
tests and then related tests. If any mismatches occur then
we are submitting the bug report to the lead.

Hi,
    In the Regression Testing we test apply the test case
again on the application which we applied previously and we
test whether the errors are being fixed or it is causing to
some new errors.We also check whether it affected the
functionality of the software.

nitin9360@yahoo.com

Regression testing is nothing but, retesting the modified
build to estimate the bug fix work and the occurances of
side effects in the build. 

  First we are conducting test on failed and then passed
tests on modified build and then on related tests.

Testing the product accross the builds is called the 
Regression Testing.

The process is :

The QE is given with build 1 and during testing he found 
some of the areas are not working and those are identified 
as bugs and he registered the bugs against that build.
Accepting that the dev. team address/fix all or some of 
those bugs and they will release a new build for testing.

Now from build2 the method of testing is bit different..
1. Verifying the fixes (TBV - To Be Verified).
2. Identify the cases affected by the fix.
3. Executing some % of Legacy cases (Cases perfectly work 
in Previous build). 
3. Test Cases developed and ready to execute for new 
functionality area.

The above process continues till Release Candidates.

Note : The bugs raised in the previous build should be 
converted to Test cases for the next build.