Vista Backup size growing too big

I have about 4GB of data that gets backed up daily using the vista backup.
Backup location is on an separate drive on a shared computer. In general it
works ok. My problem is that the space it is taking up on the bakup drive is
growing too big too fast. It is now taking uo 40GB of space, and this is
just from 6 months of daily backup. At this rate I will have to buy a bigger
hard drive, hich seems a waste, since i only need 4gb of backups. My guess
is that because it is incremental, it is growing too big. The main files
that are large that change daily are my outlook .pst files and our quickbooks
database.

My goal is to reduce the backup files to a more manageable size else I will
have to buy more hard drives....

My question is:

1 - Can I reset the backups to start over from scratch and delete the old
backups? If so, how?

2 - Is there a way to just delete the very old backups, while keeping the
most recent; I mean there is no reason why I need incremental backups that
are 6 months old.

3 - Is there a way to programatically only have it retain the last months
worth of incrementals?


Thanks,

Dave