Dell inspiron 570 memory upgrade issue

Hi

I recently acquired a Dell inspiron 570 second hand and debating upgrading it.
On inspection of motherboard I discovered one of the DIMM slots is damaged DIMM 1
broken clip and broken teeth.

System can take 8 Gb 4 DIMM slots 2gb each

My current configuration is this
Current setup, everything fine

DIMM 4 2GB EPBJ21UE8BDF0-DJ-F
DIMM 3 empty
DIMM 2 2GB EPBJ21UE8BDF0-DJ-F
DIMM 1 damaged

I would like to upgrade DIMM3
I placed a SINGLE LONE memory modules in PC as a test got following results

DIMM 4 BOOT
DIMM 3 no BOOT blue light post failure
DIMM 2 BOOT
DIMM 1 n/a

Also I have a 1GB stick which I placed in DIMM 3 with DIMM2 and DIMM4 occupied but this also failed POST this stick is fine.

The service manual says

Dell™ Inspiron™ 560/570 Service Manual
Recommended Memory Configuration see page 27
570

one RAM module = DIMM 4
two RAM module = DIMM 4 and 3
three RAM module = DIMM 4 ,3,2

http://downloads.dell.com/manuals/common/inspiron-560_service%20manual_en-us.pdf


Does this mean DIMM 3 is also damaged.

Should a Dell Inspiron 570 with a SINGLE RAM module in DIMM 3 boot?
Should a Dell Inspiron 570 with three RAM module in DIMM 4 3 2 boot?
Can I upgrade here?

Thanks