DHCP & DNS DYNAMIC UPDATING

Hello I have two specific questions.

I am using Windows 2003 DHCP / DNS and XP Clients. The DHCP server is a
memember of the DNSUPDATEPROXY group. The DNS Server is set to only allow
Secure Updates. The XP Client as expected registers it's A record itself and
asks DHCP to register its PTR record.

Q1) In DHCP If I have the box ticked "Always Dynamically Update A & PTR
Records", surely the A record will fail to register as it will not be the
owner of the A record, the XP client is. Is this correct?

Q2) If I also have Discard A & PTR record when lease is deleted", will the
DHCP Server have authorization to remove the A record as once again it
belongs to the xp client?

Many Thanks in advance

Mark