Hi, I've got an Asus T2 AH1 system. I upgraded my hd 2400 xt to a hd 5450.
The problam is if I run the PC with hd 5450, the BIOS dosen't see my HDD.
I have no clue what can bee the issue.
The PSU upgrated to 500W.
Yeeh, and only ones it started properly, I done nothing just switched off, and on, and, now it is "blind"
Most likely the problem is exactly what you posted in the title. The HD 2400 xt card is a PCIe x16 (version 1.0) and the HD 5450 card is PCIe x16 2.0. On many older systems the PCIe x16 2.0 cards will not run on the version 1.0 PCI x16 slots. Sometimes you can get a BIOS update to fix the problem but not always. I had this problem on an older computer and the fix was to get a HD 4350 Card(PCIe version 1.0) instead.
Can you post a little more info. about your system specs? I.E. MOBO, CPU, RAM, HDD, PSU, Case.
Also, are you actually getting anything on the display with the HD 5450 installed? The system is probably not getting far enough through the POST to start reading the HDD because it is failing to initialize the graphics card.