So, I should upgrade my graphics card? But then why is Sims 2 the only game I have problems with?  What ATI should I get? Is there any other way to solve my problem than getting a new card?

Yes, I have downloaded both.
I don't think that's the problem. The game worked fine for over a year with the same everything and I had no problems until a several months ago.

The only eps I have are University and Nightlife.
My Specs:
Windows:               Windows XP5.1 (Build 2600) Service Pack 2
Internet Explorer:     7.0.5730.11
Memory (RAM):          959 MB
CPU:                   AMD Athlon(tm) 64 X2 Dual Core Processor 3800+
CPU Speed:             2002.4 MHz
Sound card:            Realtek HD Audio rear output
Display Adapters:      NVIDIA GeForce 6150 LE | NetMeeting driver | RDPDD Chained DD
Screen Resolution:     1280 X 1024 - 32 bit
:                      
Network Adapters:      NVIDIA nForce Networking Controller #3 - Packet Scheduler Miniport
CD / DVD Drives:       E: LITE-ON DVDRW SHW-160H6S
:                      
COM Ports:             COM3
LPT Ports:             
Mouse:                 3 Button Wheel Mouse Present
Hard Disks:            C:  224.6GB | D:  8.3GB
Hard Disks - Free:     C:  125.2GB | D:  599.3MB
USB Controllers:       2 host controllers.
Firewire (1394):       1 host controllers.
:                      
Manufacturer:          Phoenix Technologies, LTD
Product Make:          ER900AA-ABA a1430n
:                      
AC Power Status:       OnLine
BIOS Info:             ATAT COMPATIBLE  020906  HPCPC  42302e31
Time Zone:             Central Standard Time
Battery:               No Battery
Motherboard:           ASUSTek Computer INC. NAGAMI
Modem:                 Agere Systems PCI-SV92PP Soft Modem

I've had the D3DERR_NOTAVAILABLE error for about 8 months now. The game worked fine for about a year and a half but then this came up. I have the latest drivers and reinstalled DirectX just recently but it didn't help. I have also removed custom content and the My Documents user files. DirectX Diagnostics says everything is fine. I have University and Nightlife. It crashed occasionally with University and almost right away with Nightlife. Here's my error log. Please help me!