Hi guys; my desktop became regular XFCE just like xubuntu 12.04 without me doing anything,how can i get it to change to default Mint 17.1rebeca XFCE

Please post the result of the command:
so that we can see what you have.

frank@DELL-DIM4500 ~ $ inxi -Fzx
System: Host: DELL-DIM4500 Kernel: 3.13.0-37-generic i686 (32 bit, gcc: 4.8.2)
Desktop: Xfce 4.11.6 (Gtk 2.24.23) Distro: Linux Mint 17.1 Rebecca
Machine: System: Dell product: DIM4500
Mobo: Intel model: D845EPT2 version: AAA83421-107 Bios: Intel version: A03 date: 07/18/2002
CPU: Single core Intel Pentium 4 CPU (-UP-) cache: 512 KB flags: (sse sse2) bmips: 3986.99 clocked at 1993.498 MHz
Graphics: Card: NVIDIA NV34 [GeForce FX 5500] bus-ID: 01:00.0
X.Org: 1.15.1 drivers: (unloaded: fbdev,vesa) FAILED: nouveau Resolution: 1280x1024@60.0hz, 1280x1024@60.0hz
GLX Renderer: Gallium 0.4 on NV34 GLX Version: 1.5 Mesa 10.1.3 Direct Rendering: Yes
Audio: Card: Creative Labs SB Live! EMU10k1 driver: snd_emu10k1 port: d400 bus-ID: 02:02.0
Sound: Advanced Linux Sound Architecture ver: k3.13.0-37-generic
Network: Card: Realtek RTL-8100/8101L/8139 PCI Fast Ethernet Adapter driver: 8139too ver: 0.9.28 port: d800 bus-ID: 02:00.0
IF: eth0 state: unknown speed: 100 Mbps duplex: full mac: <filter>
Drives: HDD Total Size: 200.1GB (2.6% used) 1: id: /dev/sda model: ST3160021A size: 160.0GB
2: id: /dev/sdb model: WDC_WD400BB size: 40.0GB
Partition: ID: / size: 145G used: 4.9G (4%) fs: ext4 ID: swap-1 size: 2.15GB used: 0.00GB (0%) fs: swap
RAID: No RAID devices detected - /proc/mdstat and md_mod kernel raid module present
Sensors: None detected - is lm-sensors installed and configured?
Info: Processes: 145 Uptime: 12 min Memory: 411.4/2015.2MB Runlevel: 2 Gcc sys: 4.8.2 Client: Shell inxi: 1.8.4
frank@DELL-DIM4500 ~ $

According to that you have Mint 17.1 with the xfce desktop.
Could you be more specific about the problem?

Thanks sorry for the delay;I get this Screen, see pic attach; what changed; the task bar moved up

Attached Thumbnails

 

So... you don't want the taskbar at the top?

It's not i don't like it this way, i do, but i'd like also to know how it did it by itself!