I just upgraded my power supply to an Antec neopower500w. The system boots up to windows fine; but the dvd-combo drive stops working, in fact pressing the tray-open button does nothing. One more thing that seems to be wrong is that the HDD Led is always on, even when the harddrive is not being accessed.
 
These things never happended with my old 430watt.
 
Also upgraded to a hd4850 btw.
 
SPECS:
core2 e6550 2.33ghz
2x1gb ddr-800
1 sata HDD
1 ide dvd drive  
AmD 4850
3 case fans
 
Even more weird is once I disconnected all my case fans the dvd drive works on boot up until I see the XP loading screen. So do you think it's my new power supply's problem?
Thx for reading.

What's the mobo? I would triple-check your cable connections. HDD LED always on can mean wrong polarity. Don't be surprised that the manual can be wrong sometimes.
 
What's the make & model of the psu?
 

 
http://ati.amd.com/products/radeon [...] ments.html

You might have a faulty IDE cable.  I only say that since you say the HD led is not acting like it should.
 
Try running everything as normal, but disconnect the IDE cable.

Faulty IDE cable, loose cable connection, wrongly selected master/slave for dvd if You are using IDE cable which is meant for CS(cable select). Since You did an upgrade I would say You moved or damaged cable in process. 1.Check cable connections,
2.Disconnect dvd and check if hdd led is still on, if not  
3. Try another IDE cable.