Help with my computer! Low performance.

[Beefeater]

The 420 is a PCI-E 2.0 (x16 lanes) format. That's the standard for PC's these days (PCI Express). The PCI, AGP, and VESA lines got phased out of production a long time ago, so pretty much anything made since around 2006 and up should list as PCI-E format and should work--to some extent. The exception may be ones that specifically call for PCIE 2.1 or 3.0 required, which you likely would only encounter on the primo cards at this point. They may still work, but not at full throttle. So long as you are staying in the more "affordable" lines, you shouldn't have an issue.

One of the bigger challenges will be whether it will fit (some are ridiculously long), and whether your power supply can provide the extra power it needs. The motherboard may only provide up to 75 watts through the PCI-E slot, so they will have one or more extra power ports on them for a dedicated extra 75-230 watts of power. So, if you go to far up the performance chain, you may need a stronger power supply depending on what you already have. Basically, if you have less than a 650W power supply, you may need to upgrade if you get something above the midrange tier of cards on that passmark list.

Edit:
EEP! just looked at your PDF. Looks like they cut corners on the PSU front... 250W. It's a high efficiency one, but you are going to need something stronger if you put in a performance card, which may be a problem if it doesn't have the standard-sized clearance for a larger PSU to go in there. You may want to find a PC-Geek friend to go through the case to make sure you can make the kind of upgrades we're looking at--may be better off getting a different system.

Meh okay... well I guess I'll have to save up for a whole new computer then...
Thanks for the help though.
Unfortunately I really don't have anyone here who could have a look at my computer :/


Edit: Well... Could I find any that would work anyways or is it impossible to find something like this?
Could a computer store help?