The PNY is low density. The Hyundai may be higher density, depending on capacity. It all depends on the motherboard, as to whether this might be a problem. It usually is not, but on certain boards, it can be.
Can you borrow memory modules from anyone?
You should actually be able to test by running first the 512 to a boot. Then remove it and run the 256. Run Memtest85 on each alone for 7 passes.
Look at all the details on your board website forum.
Here is the deal, the way we see it. We work on a tremendous number of Compaqs... every day... from Wal-Mart, Best Buy, Circuit City, Costco, Sams Club and so on. In our opinion, they are not great machines because they have weak motherboards in many models.
Your Presario SR1610NX is designed to use DDR PC2700, DDR PC3200, and will work well with DDR PC4000. It will handle 4 GB of DDR RAM, but usually reports out only 3.6 GB of it when full.
Your computer came with 256 MB DDR333 PC2700, or DDR400 PC3200 of Hyundai low density, low priced Value Ram memory... unless yours was unusual.
You need 1 GB, in two identical 512 MB DDR400 PC3200 or better modules, or better yet, 1 GB in one module.
Ideally, you could have at least 2 GB in two 1 GB DDR466 PC3700 or DDR500 PC4000, or two 2 GB modules of DDR500 PC4000 128Meg X64
You can get two 512 mb Kingston or Corsair modules at
www.zipzoomfly.com for $29.90 each with free shipping.
You can get two 1 GB DDR400 PC3200 Corsair modules for $52.50 with free shipping... so it would be costly but it might be worth it at $105.00 for two GB... but not bad, either.
The thing we don't know is if your motherboard is solid, because a lot of those Compaq Presarios with 4 GB capacity have been trouble.
I do, however, strongly believe, that you need better memory to survive this... and that can be done for $59.80. They can be a matched pair. You can sell the old memory for $20... end cost $40 if you are on a tight budget.
We still don't know if memory is the problem, but you need to start testing those other components while using better memory. And whatever else happens, that memory will make a difference... you will be able to sell it on eBay for what you paid, or more.
If it were mine, I would get another computer that is not a Compaq, Sony, eMachines or low priced HP... but money is money.
If you are a gamer, and keep this computer, I would buy better memory from the same vendor, than what I have showed you here. and I would fill up all slots with PC4000.
Good look to you. We will be following your progress. We are confident you will work it out, and we are looking forward to learning from you.