Solved Graphics Card Upgrade Problem-Nvidia GTS450

I've been trying for some time to resolve an issue whereby my attempts at upgrading the graphics card in my desktop PC have been unsuccessful. The reason for the upgrade is that the existing card (Nvidia GeForce 210) isn't quite powerful enough to display all the graphics content in a particular program. The PC is an older model, therefore for the upgrade I have chosen a Nvidia GeForce GTS450 as it came onto the market shorty after the PC was manufactured (2009). The GTS450 should be compatible with the computer, however there is a significant problem when trying to run it after installation. I opened a support ticket with Nvidia Tech Support, however the advice which I was given has not led to success. I'm hoping that there may be members on this forum who may be able to offer a diagnosis and a solution if one exists.
The PC spec. is as follows:
Dell Vostro 220 running Windows 10 64-bit.
Intel Core 2 Duo E8400@3.00GHz.
8GB RAM. 1TB hard drive.
2xPCI slots, 1xPCIe slot. 700W power supply with 38A DC output (upgrade from original 300W PSU).
Motherboard=Dell G45 M03 version A02.
BIOS=Version 1.3.0 (last update issued).
The existing GeForce 210 occupies the PCIe slot. It has no built-in fan or 6-pin power socket. The card works fine apart from it not being able to fully display all the content in a program, hence the need for an upgrade. The GTS450 card has both a fan and 6-pin power socket. I have downloaded and installed a driver which was suggested to me by Nvidia Tech Support. Here's what happens when I replace the GeForce 210 card with the GTS450 and power up the computer:
The fan in the card spins. The hard drive makes a brief whining noise as it normally does. The PC doesn't boot into Windows, therefore there is no output from either the DVI or HDMI ports on the card. The usual amount of ongoing mechanical noise from the hard drive is absent. It seems that the graphics card prevents the hard drive from functioning, therefore I'm unable to get into the system in order to get the card and driver to communicate. When I reinstall the GeForce 210 card, everything works fine again.
I purchased the GTS450 from an Ebay seller who assures me that the card was tested and working before despatch. The most recent advice from Nvidia Tech Support was that I upgrade the power supply with a replacement which at least matches the minimum DC input requirement for the card (22A). I have done that without success.
I have seen numerous references to changing settings in either the BIOS or CMOS. Unfortunately, I don't have experience of making such changes, therefore I wouldn't know what to look for.
If any advice regarding possible solutions is out there, I'd be very grateful to receive it.

Hello and thanks for your response. I followed the link which confirms that the GTS450 card is too weak for the processor. Whilst I don't completely understand the technicalities, it seems that the GTS450 card isn't compatible with the CPU. I'm somewhat confused as to why the GeForce 210-which doesn't have a 6-pin power socket and came out before the GTS450-would be a stronger card. Also, would a graphics card which is too weak cause the hard drive to become disabled? What specific specifications should I be looking for in order to ensure that I obtain a graphics card which isn't too weak?

Hello, so as well as having an incompatible graphics card upgrade, I may also have an incompatible PSU upgrade. I’m not doing very well, am I? I had no idea that there was so much involved in upgrading a graphics card. The original PSU was a Liteon 300W model PS-6301-6 with 18A max at 12v+. The GeForce 210 card worked fine with it for a considerable length of time. I didn’t know that an upgraded card may require an upgraded PSU. Wheh I discovered that the GTS450 wouldn’t work, I contacted Nvidia, who’s representative advised me that I would need a PSU with a minimum DC output of 22A. I replaced the PSU with a LMS Power X700 model with a stated DC output of 38A. It wasn’t particularly expensive, but had the connectivity I needed, including the 6-pin PCIe connector for the card upgrade. The PSU was described as being 700 watt. It sounds as though PSU’s arent always what they claim to be. I have researched later Nvidia graphics cards which are reportedly compatible with my CPU, however I’m unsure as to whether to proceed now that there appears to be a question mark over the suitability of the replacement PSU.

I knew the PSU wasn't the best quality, however I didn't know that there was a risk that it wouldn't do what I bought it to do, i.e. to power a graphics card. One of the attractions-apart from the quoted power and DC output of the PSU-was the 6-pin PCIe connector. I'd really like to know why the graphics card, when installed, disables the hard drive. Is there anything to be gained by disconnecting other components being powered by the replacement drive? (2 DVD drives, a Firewire card, a USB3 card and a second hard drive). It's unlikely that I'll be able to test the card on someone else's PC.
The GTS450 card has the name Palit attached to it.

I have the opportunity to buy a used Aerocool Integrator 600W 80+ Bronze power supply for £35.00. Is that likely to be of sufficiently good quality to power the GTS450 card?

I appreciate your help and will now conclude the thread.