Users complain that system runs slow when mysqldump is in progress The MYSQL database (ibdata1) is of size 73 GB and is configured to run as a dedicated database server on Windows 2008 O/S for INNODB tables. 
We are running the backup using mysqldump 
mysqldump --skip-opt --quick --single-transaction --create-options --extended-insert --disable-keys --add-drop-table --complete-insert --set-charset -- compress --log-error=Proddb0635.err -u root -pjohndoe Proddb> \devNas\devNas\sqlbackup\LIVE\db\Proddb0635.sql

The backup file Proddb0635.sql is stored on a separate server from the database server.
RAM is 12 GB.
INNODB Buffer Pool size is 6 GB.
Additional mem.pool is 32 MB.
Query Cache size is 2 GB
Net buffer length is 16 M
Max. packet size 1 GB.

mysql version is 5.0.67.

When backup is not running users are happy with the performance.

When backup is running INNODB Buffer pool hit rate is high close to 100%.
There are no pending reads or pending writes. innodb wait free is 0.
CPU usage is not high min 9% to max 15 %
Query cache hit rate is low about 40% with or without mysqlbackup running. Currently Windows Task Manager  is displaying that 10GB of RAM is being used. Should I increase Query Cache with only 2GB of RAM available?
mysqlld-nt is taking 9.2 GB of RAM and mysqldump is taking 5 MB of RAM.
Alos, noted that the size of the dump file is same in presence or absence of --compress option. 

SHould I decrease the iNNODB Buffer Pool size?

Thanks
There is a known issue in Windows, that when you push a large file to another server all the memory ends up getting allocated to the System cache instead of the user processes.  You can look  in the Physical Memory (MB) section of task manager to see how much memory is allocated to the system cache.

This can be solved by backing up to a local disk, then having the remote machine pull that file.