ATI Radeon HD 4650 – Screen flickers

I will start with my system specs:

Motherboard - Hewlett-Packard HP d530 SFF
OS - Windows XP Professional SP3 with all updates installed
RAM - 1GB Kingston
Monitor - Samsung SyncMaster 703DF(X)/753DF(X)/783DF(X)/MagicSyncMaster CD173A(T)
Drivers installed from CD
HDD - WDC WD1600JB-00GVA0 (160GB, 15mb/sec read)
CPUID Manufacturer - GenuineIntel
CPUID CPU Name - Intel(R) Pentium(R) 4 CPU 2.80GHz
CPU Type - Intel Pentium 4, 2800 MHz (21 x 133)
CPU Alias - Northwood
CPU Stepping - D1
Instruction Set - x86, MMX, SSE, SSE2
Fans - Only CPU

GPU:

Field   Value
Graphics Processor Properties   
Video Adapter   ATI Radeon HD 4670 AGP (RV730)
BIOS Version    011.021.000.006.031888
BIOS Date   04/08/09 03:25
GPU Code Name   RV730 Pro
Part Number 113-AAXXXXX-XXX
PCI Device  1002-9495 / 1458-0028  (Rev 00)
Transistors 514 million
Process Technology  55 nm
Die Size    146 mm2
Bus Type    AGP 8x @ 8x
Memory Size 1 GB
GPU Clock   165 MHz  (original: 600 MHz)
RAMDAC Clock    400 MHz
Pixel Pipelines 8
TMU Per Pipeline    1
Unified Shaders 320  (v4.1)
DirectX Hardware Support    DirectX v10.1
Pixel Fillrate  1320 MPixel/s

Memory Bus Properties   
Bus Type    DDR2
Bus Width   128-bit
Real Clock  250 MHz (DDR)  (original: 400 MHz)
Effective Clock 500 MHz
Bandwidth   8000 MB/s

I had built-in video. I wanted to upgrade my graphics card. Friend gave me an ATI Radeon HD 4650. But to do that I replaced my 300 watt PSU with 650 watt PSU (because minimum for card was 450w). And after that I pluged in this card and installed drivers from CD that came with my video card. The problem is, that sometimes while playing games (Minecraft, Euro Track simulator, Crysis etc) the screen freezes for a second and turns black (flickers). Then turns on back again but some games crashes. When screen flickers, ATI Radeon Service poops up and says that graphics card stopped to responding. I forgot that my PC is overheating. When I used built-in video card, the temps were:

AUX 40C
System 60-68C

After installing new PSU and this card:

AUX 42C
System 65C-69C

If you think that video card is overheating, well no, max video card temperature was 47,5C.
So what can be the problem?