How do I stop/disable PITR and safely clean WAL segments?

Hi,

Our production server is running PostgreSQL v8.2.3 on CentOS release 5.2
(Final).

We've setup PITR in our production server. For some reasons, after setting
up PITR, we're not able to manage and maintain it. Eventually, our WAL
archive drive (secondary drive) has become full (100% use) and additional
WAL archive segments that are to be archived got accumulated in pg_xlog/
directory itself (which is available in primary drive)

PITR SETUP DETAILS

There are 2 drives:

1. Primary drive (pgsql/data/ directory resides) is 400 GB.
2. Secondary drive (WAL archives) is 300 GB. All WAL archives are written
to this secondary drive.

Now, we've decided to stop/disable PITR.

My question is, in this situation, how do I stop/disable PITR and safely
clean up all WAL segments from both the drives?

What are the recommended/suggested ways? Experts advice/idea/suggestion on
this are highly appreciated.

Regards,
Gnanam