yes, after having my emachines for awhile, i wanted to upgrade to something better( celeron sucks) but i wanted to use the same case and PSU. I didn't find many motherborads out there to begin with, and the PSU in there wouldnt be enough, so i looked at mico PSUs. It got way too complicated, and i ended up building a mid tower with all the stuff i wanted. so like micro bell said, you are extremely limited in what you can upgrade.
AMD Athlon XP 2500+@ 200x11 - EPoX 8rda3I - Thermaltake 420watt silent PSU - 2x512MB PNY PC3200(DualChannel) - TT HSF - PNY 5900SE, 128MB DDR, 256-bit - - Toshiba SD-R5002: DVD-RW - NEC DVD-RW - 2 Antec 80mm fans - 1 Delta 92mm fan - 1 Antec 120mm fan- 1 TT 120mm fan - Windows XP Pro - WD special edition 80GB 7200 RPM- Seagate 80GB 7200 RPM 8MB cache - Onboard Sound - Onboard Ethernet
ACER Travel Mmate 4000LCi - Intel Pentium M 710 - 15\" XGA TFT - 512MB DDR333 - 40 GB HD - DVD-rom/CD-RW Drive - WLAN 802.11b/g - Winxp Home - Intel Extreme Graphics - Average Battery Life: 4-5 hours - 6.4 lbs