I am trying to put some new RAM in my old PC, which currently has a single 32mb SDRAM stick. If I put in a single 128 or 64mb SDRAM stick instead the PC fails to boot up. The monitor light turns red and everything stops. If I try to install 4 x 8mb SIMMS I get the same result. What could be the reason for this, please? The CPU is an AMD-K5-PR120, but that's all I can find.

The type and size and geography of the RAM chips matter. A lot. I would go to crucial.com and run their memory checker. It will tell you what type and size you can use. They have never failed me. Good luck.

Hard to say without having more system specs...motherboard & chipset would help 1st of all, most of those old systems only cached 64MB of RAM...there's no point exceeding that amount if you're just doing "normal computing", it'll just kill the system's performance. 2nd, you need to know the max amount of RAM supported per slot...64MB may simply be too much in a single stick 3rd, if the board takes either SIMMs or DIMMs, the SIMMs should be installed in matched pairs. There may be a jumper that has to be changed depending on which memory type you use Asus A7N8X-X 1800+ @ 8.5 x 200MHz 768MB PC3200 2.5-3-3-7 Asus A9550GE/TD 128MB WinME/WinXP Pro

Yes, if I could get the motherboard model it would help. For some reason neither of my PCs will work the Crucial RAM checker. The screen just freezes.

I don't know whether this helps, but using Belarc I get under the 'Main Circuit Board', BIOS: Award Software 4.51PG Also, I just tried the SDRAM 64mb stick again and this time it works, but only as 16mb.

"BIOS: Award Software 4.51PG" No, that doesn't help... "I just tried the SDRAM 64mb stick again and this time it works, but only as 16mb" sounds like it's either a density issue, capacity issue, or simply the wrong kind of RAM. Older boards like that used FPM or EDO DIMMs, which are different than PC66/PC100 SDR-SDRAM Try running CPUZ - download, unzip, click on CPUZ.exe: http://www.cpuid.org/cpuz.php#download Asus A7N8X-X 1800+ @ 8.5 x 200MHz 768MB PC3200 2.5-3-3-7 Asus A9550GE/TD 128MB WinME/WinXP Pro

The RAM that works, and was originally in the PC, is marked "SD32MB" and "32MBSD-P2601". With CPU-Z, the chipset comes up as Intel ID7030