How do I find out what would be the biggest HDD and RAM module that will be accepted without trial and error?
Is a bit to specific. I hope you do not mind if I answer this in general, so other readers also can apply that for their laptop models.
Lets start with the harddisk:
1) Your laptop uses a
SATA harddisk. There are currently three SATA standards, but they are all backwards compatible. Therefore any SATA harddisk currently on the market can be used.
ERROR: That was the wrong model. The tecra A4 has IDE. Drives do get faster per generation, but I can't find any recent IDE drives. Which means you are probably stuck with the current drive or an expensive upgrade to a 320GB-ish drive from a few years ago. This is probably not worth it.
2) The harddisk partitioning scheme used on most older computers is MBR. This has a limit of 2.19TiB. You will need to partition the drive differently to use a larger drive.
For PC style hardware this is usually done by partitioning it with GPT. Not every BIOS understands GPT, which means that for an older computer you usually can not boot from a GPT partitioned disk.
Thus you need any SATA HDD up to 2.19TiB.
Next, the memory.
The maximum amount of memory you can use is limited by:
- The CPU (which these days holds the memory controller)
- The chipset (esp. older ones which contained the memory controller)
- The number of copper traces on the motherboard. (Cheaper to lay less traces. The manufacturer will usually use enough to satisfy most of the market. More just isn't economical)
- The available memory modules. Both their maximum size,and number of memory slots.
Your laptop has an Pentium-M 750
which can address up to 32bit (4GiB).
Your chipset is an http://ark.intel.com/products/27717/Intel-82915PM-Graphics-and-Memory-Controller">Intel 915PM. This one has a max memory limit of 2 GB.
You can only use the lesser of these two. Your are limited 2 GB.
A sanity check on your motherboard shows that it indeed allows up to 2GB, using DDR SODIMM's at 333MHz ( PC2700 ). You will DDR(1) SoDIMMs. DDR2 and DD3 will neither fit, nor will they work it you fit them with help of a hammer.