upgrades (options)

internal
(add new hardware to your computer system)
chips (when used in sockets)
expansion cards (MCA, ISA, VLB, PCI [32/64bit], AGP ...)
  www.xlr8.com Mac (Motorola) CPU upgrade cartridges
  WinModems
mobiles (PDA, notebook, phones...)


external
(connect additional hardware to interfaces for new capabilities of your hardware)
IrDA (infrared port)
USB (universal serial bus)
LPT (parallel port / RS232)
COM (serial port)
PS/2 (serial port II)
PCMCIA (PC card slot, mostly on notebooks and mobile PDAs)
FireWire (IEEE1394 port, iLink on Sony hardware)
GeoPort (serial port)

You can find useful informations on upgrading your system at the following links:

UnofficialIBM Aptiva Support Site
IBM PS/2 computer FAQ
Intel Newsgroup Forum
Intel OverDrive Upgrade Page - List of computers that are compatible with Intel OverDrive processors.
Packard Bell Exclusive Homepage - Information on various Packard Bell systems.
PB User Web World - Packard Bell Users Group. Membership fee required.
Ray's Packard Bell Site - Info on Packard Bell, especially the 640/660 motherboards.
Tandy Retail Services - Information on computers sold by Radio Shack.
This Old 486 - Illustrated guide to upgrading a 486.
The Unofficial Aptiva Hint Page - Tips and links on upgrading IBM Aptiva computers.
Upgrade Your Pentium to a 6x86 - Tips on upgrading with a 6x86.
Upgrading to an IBM/Cyrix 6x86MX - Tips on upgrading with a 6x86MX.
VAIO Place - Info on Sony VAIO systems.