Jax, SO sorry it took me so long to reply. We had a MASSIVE storm and I lost power. -_-
Anyways, Check the bottom of the CPU for any burn or scorch marks. If there are any, it's toasted.
Packard Bells and Compaq's use a sub-standard bios that's mounted on the HDD, before the MBR. Since it's a 300 MHZ K6-2, odds are the mobo isn't a Pakard Hell custom. Look for a model number on the board itself. If you're lucky, it's probably a Gigabyte board and they, in my experience are farily reliable.
The ram is fine, so long as you use it with a Socket 7 motherboard. The ram you're using is LOW-DENSITY, PC100 SDRAM. Compaq and Packard Hell, for some odd reason, preferred using the low-density variety.
Best thing to do is remove the board from the box, place it on a static-free item, like a cardboard box and start from scratch. Take everything out of the case and plug it in one at a time. Power it on, using a ball-point pen. Since you're not getting any beeps, it could be a dead CPU or mobo, but since it's not in front of me, I can't tell you for sure.
Everyone's correct, though. Packard Bell's are crap. They were never designed well and have a notorious habit of breaking. You, if you want to venture in to the PC world, should look into getting a new mobo.
Oh, before I forget, you said that there was no video card. Is the video on the motherboard itself? If that's true, the power supply you replaced could have spiked the motherboard, killing it. If you get no beeps and nothing, but an LED for power and HDD, I say again, it's a dead mobo or CPU.
I have a compaq 450 K6-2 mobo that I'm not using. It was a 475, but started flaking out until I dropped it to a 450. It is a TRUE Gigabyte board and I reflashed the BIOS to use the Gigabyte version of the BIOS. If you need it and can pay for the shipping (if I could, I would), it's yours. I guarantee that it works, but it's not the best thing in the world. It's got onboard sound and video, but don't expect to play any serious 3D games with the chipset (it's a SIS 530).It requires low-density, PC100 SDRAM, but can handle 3 sticks at 256MB, for a maximum total of 768MB on the board. Up to 8MB is shared video memory. It's a solid board and I used it regularly for 4 years, up until last year. It was my old Amithlon box, until I got a new one. ^_^