According to the documentation, it appears so:
http://www.downloads.netgear.com/files/GDC/DGN2200/DGN2200_UM_3Feb11.pdf
I am not 100% on this however as the documentation references AP1 AP2 and AP3 rather than specific functions assuming you own 3 of the same device. You can try it since it's your friends spare, if it doesn't call tech support otherwise restore factory defaults and give it back to him.
Specific Instruction
Set up your modem router to be the base station.
(Your ISP's Modem/Router)
a. In the Wireless Repeating Function screen for your modem router, select the Enable
Wireless Repeating Function check box.
b. Select the Wireless Base Station radio button.
c. Clear the corresponding Disable Wireless Client Association check box (make
sure it is not selected).
d. Enter the MAC addresses for AP 2 and AP 3 in the Repeater MAC Address 1 and
Repeater MAC Address 2 field.
e. Click Apply.
2. Set up AP 2 and AP 3 to be wireless repeaters.
(The Netgear DGN2200 N300) enables wireless repeating functionality
a. In the Wireless Repeating Function screen for AP 2 and AP 3, select the Enable
Wireless Repeating Function check box.
b. Select the Wireless Repeater radio button.
c. Clear the corresponding Disable Wireless Client Association check box (make
sure it is not selected).
d. Enter the MAC addresses for your modem router in the Base Station MAC Address
field.
e. Click Apply.
3. Verify the following for all access points:
• Each access point operates in the same LAN network address range as the LAN
devices.
As a side note you may also have to disable DHCP for the repeater since the ISP's modem/router should be controlling this, but shouldn't hurt either way, unless you want him to access your network PCs as the subnet may change due to IP conflicts between routers. The ISP modem should configure as 192.168.1.1 and the repeater may configure to 10.1.10.1 or vice versa.
You should also configure it via a WIRED connection to the router. After config it can be unplugged and tested accordingly.