How to Disable Power Save Mode

I'm having monitor problems: the screen becomes black and a Power Save Mode message temporarily comes on. I would like to disable it. How do I do it? botz

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Dell-Dimension 8300 Series
Date of Purchase September 9, 2003
Chipset PCI Intel I875P at 533 MHz (support processor with bus system at 800 MHz)
BIOS Version: A02
Memory DDRSDRAM Dual Channel
BUS AGP 8x, 8 USB 2.0, 4 PCI
Norton Anti Virus 2003
10/100 Pro Ethernet (RJ 45 only)
Windows XP Home SP1 Version 5.1.2600
Intel Pentium 4 at 3.2 GHz, bus system at 800 MHz
2048 Mo DDR SDRAM (4 x 512)
Floppy Drive 3.5"/1.44 Mo
240Go Serial ATA RAID 0 Stripe (2 hard disks x 120 GB 7700rpm with DataBurstTM cache)
Dell Monitor 18" 1800FP Flat Ultrasharp (DVI)
Video Card ATI Radeon 9800 Pro 128 Mo DDR (exit TV support DVI and Dual Display)
Burner DVD + RW 4x/CDRW (12x/10x/32x) and Player DVD ROM 16x with decoder software MPEG 2 (2 players 2baies 5"1:4)
Sound Card Sound Blaster Audigny 2 (Port IEEE 1394 included)
Altec Lansing ADA995 - 5 x 20 W and base 100 W (THX)
Modem Card (DATA/FAX) 56kbps V92
Mouse Dell PS/2
Microsoft Works 7.0
Logitech Dual Action USB Gamepad
Microsoft SideWinder Force Feedback 2 Joystick