Slow DVD writing speed at 5:40 PM

The most common reason for this is your DMA is not enabled

Turn your DMA modes on in the Device Manager

• Press Window key + Pause Break (System properties)
  
• Control + Tab 3 times (Hardware Tab)
  
• Alt + D (Device Manager)
  
• Tab, type I (until IDE ATA/ATAPI controllers is selected)
  
• Right arrow to expand
  
• Type P (select Primary IDE Channel)
  
• Enter (wait until Primary IDE Channel Properties appears)
  
• Control + Tab to Advanced Settings Tab
  
• Change your Transfer Mode(s) to DMA if available (chances are, it is set to PIO only)
  
• Do that for both Device 0 and Device 1, and repeat for any other Primary IDE Channels that you have
• Click OK
• And then open the Secondary IDE Channel listing. Do the same as above
• Restart

By editing the Registry you can do it in following way -

Run REGEDIT. Go to the following key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}
It has subkeys like 0000, 0001, 0002, etc. Normally 0001 is the primary IDE channel, 0002 the secondary, but other numbers can occur under certain circumstances. You have to go through these subkeys and check the DriverDesc value until you find the proper IDE channel.
Delete MasterIdDataChecksum or SlaveIdDataChecksum, depending on whether the device in question is attached as master or slave, but it can't actually hurt to delete both. Reboot. The drive DMA capabilities will be redetected.
Note that many CD and DVD drives only use UDMA-2, because their data rate is much lower than that of a hard disk. This is normal.