4745454b :
Spentshells, no.
The FX5200 was an AGP/PCI card. The PCIe version was called the FX5300 and was SUPER rare. It's nice you say he means something, but he wrote 8x slot. While there are 8x PCIe slots, as I mentioned above they aren't common. What is common is what he wrote. He has an "8x" slot/card, and its currently running an FX5200. This means we are talking AGP here, not PCIe. While true we won't know for sure until he posts a motherboard, I find it far more likely that he has AGP over some odd PCIe slot.
I actually had/have (it doesn't work) pcie 5200 fx it came oem with a dell (canada) or this soldered biostar board when they used to offer "business solutions" but i see your point
If the slot was the wrong size despite not being knowledgeable I am sure the op is able to guage the length of a slot by looking at it, Hes asking for help not unable to see.
Since he said
Can I insert a x16 Radeon 5450 into a x8 slot ?? If so what are the disadvantages?
We are all making assumptions only mine makes the most sense without further information while I do appreciate you practicing your psychic abilities while chastising me for making a basic assumption the op is able notice the size of the slot or be even the least bit aware of the information he is dealing with.
As for the 8x pcie 5200fx which never existed at all ever at any time I would say that is a shite side more rare than a pcie x16 times fx5200
lets all practice logic together