Question Question Appealing for three different Manufacturer's laptop hardware

I started to working with three laptops with different kind of missing hardware. I list them down there seperately and hopefully somebody can help me to fix them after I get information about right components model bought.

Acer Aspire 3620
  • What's the maximum amount of RAM memory that I can attach to motherboard. There's now 1024MB. What type of pins, or RAM -adapter model I should look at my local PC Component Dealer's shop?
  • There's no HDD -drive installed or previous user have removed it. What type of HDD Drive I should buy for this model? (60 GB is enough for this computer.)

Acer Aspire 3020
- Same question equalled to previous Acer machine appealing for RAM, what's the Maximum and what type of pins and adapter model? Now there's only 512 MB and Linux Mint Live CD Installation takes forever.

HP Compaq nx7400

  • What's the maximum amount of RAM memory that I can attach to motherboard. What type of pins, or RAM -adapter model I should look at my local PC Component Dealer's shop?
  • What type of attachement for the HDD-drive there's in Mother Board compatible with this model?

Targa (Unknown Model)
What kind of AC Adapter is Compatible for this laptop manufacturer's machine?

This is my very first posting down this forum even I've been in PC both of Hardware and Software and Networking since my childhood. Hopefully somebody can help me and in the future I can give some help to back to somebody else too.
 
Thanks! I discovered this topic by Googling Up my Laptop Manufacturer¨s name and model number as keywords and cleared my needs.

My Acer laptop got ATA 100 bus for the HDD (It¨s old one), can I attach SATA Hard Disk to ATA 100 -bus straight, or by converting something?

How does it is range about price for small ATA 100 HDD nowdays on used component markets? (60-80 GB ATA 100 -cable attachement). I got to look at eBay I think.